applet has a 5 second delay

Actually it is more around 2 seconds...
After a little digging in the sources I found that the evildoer is not the applet but netbook-launcher, even if you can argue whether it is the best way to go through the whole initialization and startup stuff of netbook-launcher only to hide all windows (and show the "Favorites").
I guess a dbus interface would probably be the best thing to implement.

Since the go-home-applet is a central point of the user interface experience it might have a bad effect on (new) users causing them to say "Linux/Ubuntu/UNR/go-home-applet is slow on my netbook, while Windows was/is much faster". I don't think we should scare people away because of something like this...

A typical invocation of netbook-launcher from shell looks like this, where the most time seems to be spent before the "Low graphics mode" line.

$ time netbook-launcher -s

(netbook-launcher:14126): GLib-WARNING **: g_set_prgname() called multiple times

(netbook-launcher:14126): GLib-WARNING **: g_set_prgname() called multiple times
(netbook-launcher:14126): libnetbook-launcher-DEBUG: CONFIG: Low graphics mode: False
(netbook-launcher:14126): libnetbook-launcher-DEBUG: CONFIG: Font dpi: 96.000000
(netbook-launcher:14126): libnetbook-launcher-DEBUG: CONFIG: Font changed: Sans 10

(netbook-launcher:14126): libnetbook-launcher-DEBUG: CONFIG: Connecting to ConsoleKit for suspend/resume restarting

real 0m2.129s
user 0m1.348s
sys 0m0.460s

It seems that netbook-launcher is already using dbus to show the favorites. It might not be that hard to copy the relevant sections to the applet.

The delay is more like 3.5 sec on my system, but it's enough to be annoying. I notice that the delay only occurs when I am using metacity, and disappears when I use compiz. My uninformed guess is that netbook-launcher or gohome-applet are waiting for the transition effect to complete, when there is in fact no transition effect. Does that make sense?

Hm... the exact timing varies for me, but I experience this as well.

A workaround for affected users: Replace go-home-applet with the "Show Desktop" applet. Same functionality, but instantly responsive.

To be exact, not same functionality: you can't drag and drop an url there to create a favorite.

Maybe someone can work on a patch so that in addition to calling "netbook-launcher --show-favorites", it should hide all the windows just as the show-desktop applet does. This way, all the windows (except the netbook-launcher itself) will hide instantly and then 2-5 seconds later, the favorites will appear if it isn't already.

The show desktop applet is written in Vala and uses libwnck to show/hide the windows, so it shouldn't be too hard.

All you would probably need to do is in the applet.c file:

#include <libwnck/libwnck.h>

And then in the on_button_press function on line 192, adding:

WnckScreen* screen = wnck_screen_get_default ();
if( !wnck_screen_get_showing_desktop (screen) ) {
    wnck_screen_toggle_showing_desktop (screen, TRUE);
}

I haven't tested it, but it might work well.