vagrant@devstack:~$ heat stack-show f5a06c66-3d1d-4ecd-9ef9-d0e3a25c4e29
+----------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Property             | Value                                                                                                                                                           |
+----------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+
| capabilities         | []                                                                                                                                                              |
| creation_time        | 2014-11-11T17:42:47Z                                                                                                                                            |
| description          | Basic app deploy.                                                                                                                                               |
| disable_rollback     | True                                                                                                                                                            |
| id                   | f5a06c66-3d1d-4ecd-9ef9-d0e3a25c4e29                                                                                                                            |
| links                | http://10.0.2.15:8004/v1/1cb3982d28cc480cbf72cfdfe90e5e6f/stacks/coreos3-nov11-df718e8a-14c3-4756-95d7-9e9cd2a8a4bd/f5a06c66-3d1d-4ecd-9ef9-d0e3a25c4e29 (self) |
| notification_topics  | []                                                                                                                                                              |
| outputs              | [                                                                                                                                                               |
|                      |   {                                                                                                                                                             |
|                      |     "output_value": "",                                                                                                                                         |
|                      |     "description": "The public IP address of the newly configured Server.",                                                                                     |
|                      |     "output_key": "public_ip"                                                                                                                                   |
|                      |   },                                                                                                                                                            |
|                      |   {                                                                                                                                                             |
|                      |     "output_value": "http://:5000",                                                                                                                             |
|                      |     "description": "The URL for the Server.",                                                                                                                   |
|                      |     "output_key": "URL"                                                                                                                                         |
|                      |   }                                                                                                                                                             |
|                      | ]                                                                                                                                                               |
| parameters           | {                                                                                                                                                               |
|                      |   "OS::stack_id": "f5a06c66-3d1d-4ecd-9ef9-d0e3a25c4e29",                                                                                                       |
|                      |   "OS::stack_name": "coreos3-nov11-df718e8a-14c3-4756-95d7-9e9cd2a8a4bd",                                                                                       |
|                      |   "key_name": "",                                                                                                                                               |
|                      |   "image": "coreos",                                                                                                                                            |
|                      |   "du_image": "10.0.2.15:5042/nodeus",                                                                                                                          |
|                      |   "flavor": "m1.small",                                                                                                                                         |
|                      |   "port": "5000",                                                                                                                                               |
|                      |   "app_name": "coreos3-nov11"                                                                                                                                   |
|                      | }                                                                                                                                                               |
| parent               | None                                                                                                                                                            |
| stack_name           | coreos3-nov11-df718e8a-14c3-4756-95d7-9e9cd2a8a4bd                                                                                                              |
| stack_owner          | None                                                                                                                                                            |
| stack_status         | CREATE_COMPLETE                                                                                                                                                 |
| stack_status_reason  | Stack CREATE completed successfully                                                                                                                             |
| template_description | Basic app deploy.                                                                                                                                               |
| timeout_mins         | None                                                                                                                                                            |
| updated_time         | None                                                                                                                                                            |
+----------------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+

Notice that the the output_value for "public_ip" and "URL" are empty.  Here is the part of the "output" section of the heat template that I am using:

outputs:
  public_ip:
    description: The public IP address of the newly configured Server.
    value: { get_attr: [ compute, accessIPv4 ] }
  URL:
    description: The URL for the Server.
    value:
      str_replace:
        template: http://%host%:%port%
        params:
          "%host%": { get_attr: [ compute, accessIPv4 ] }
          "%port%": { get_param: port }

Notice that I am using the "accessIPv4" attribute of heat to get the public_ip of the spun up server.

Based on the output of heat stack-show command, it looks like the "accessIPv4" attribute is not providing the IP address of the spun up server.

This is confirmed by 

vagrant@devstack:~$ nova list
+--------------------------------------+---------------+--------+------------+-------------+----------+
| ID                                   | Name          | Status | Task State | Power State | Networks |
+--------------------------------------+---------------+--------+------------+-------------+----------+
| f7c9825a-5adc-4a99-a80e-45923056df6e | coreos3-nov11 | ACTIVE | -          | Running     |          |
+--------------------------------------+---------------+--------+------------+-------------+----------+

Notice that the there is no value for "Networks" attribute.

Notice that in the path that used nova boot directly, I had to create nova-network first and then use that within the "nova boot" command. Looks like I would need to do something similar within the heat template.