dual monitors: ugly mirror resolution, fn-f7 does not propose stretching the desktop over the 2 monitors

I have 2 monitors.

On login, Unity gives me the same image on both monitors, in a suboptimal resolution for both (everything is blurry). xrandr gives:

Screen 0: minimum 320 x 200, current 1152 x 864, maximum 8192 x 8192
LVDS1 connected 1152x864+0+0 (normal left inverted right x axis y axis) 303mm x 190mm
   1440x900 60.0 + 59.9 50.0
   1360x768 59.8 60.0
   1152x864 60.0*
   1024x768 60.0
   800x600 60.3 56.2
   640x480 59.9
VGA1 connected 1152x864+0+0 (normal left inverted right x axis y axis) 430mm x 270mm
   1680x1050 60.0 +
   1280x1024 75.0 60.0
   1152x864 75.0*
   1024x768 75.1 60.0
   800x600 75.0 60.3
   640x480 75.0 60.0
   720x400 70.1

Cycling modes with Fn-F7 (this is a Lenovo T410s laptop) gives :
- only the right (external) monitor at its optimal resolution
- only the left (internal) monitor at its optimal resolution
- the above suboptimal mirror.

I expect:
- that the proposed mirror setup would use the preferred resolution for both monitors, which is possible (see below)
- to be proposed a setup with one desktop that takes both monitors (using their preferred resolution)
- that the setup chosen by default with my 2 monitors would be a good-looking one (either mirror or stretched with preferred resolutions).

This used to work in previous releases (both items), though maybe only for Unity 2D since this it what I was using then.

My workaround to get a stretched desktop:
 /usr/bin/xrandr --output LVDS1 --mode 1440x900 --output VGA1 --mode 1680x1050 --right-of LVDS1

Which gives:

  Screen 0: minimum 320 x 200, current 3120 x 1050, maximum 8192 x 8192
  LVDS1 connected 1440x900+0+0 (normal left inverted right x axis y axis) 303mm x 190mm
     1440x900 60.0*+ 59.9 50.0
     1360x768 59.8 60.0
     1152x864 60.0
     1024x768 60.0
     800x600 60.3 56.2
     640x480 59.9
  VGA1 connected 1680x1050+1440+0 (normal left inverted right x axis y axis) 430mm x 270mm
     1680x1050 60.0*+
     1280x1024 75.0 60.0
     1152x864 75.0
     1024x768 75.1 60.0
     800x600 75.0 60.3
     640x480 75.0 60.0
     720x400 70.1

And to get a nice-looking mirror desktop:
 /usr/bin/xrandr --output LVDS1 --mode 1440x900 --output VGA1 --mode 1680x1050 --same-as LVDS1

Which gives:

  Screen 0: minimum 320 x 200, current 1680 x 1050, maximum 8192 x 8192
  LVDS1 connected 1440x900+0+0 (normal left inverted right x axis y axis) 303mm x 190mm
     1440x900 60.0*+ 59.9 50.0
     1360x768 59.8 60.0
     1152x864 60.0
     1024x768 60.0
     800x600 60.3 56.2
     640x480 59.9
  VGA1 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 430mm x 270mm
     1680x1050 60.0*+
     1280x1024 75.0 60.0
     1152x864 75.0
     1024x768 75.1 60.0
     800x600 75.0 60.3
     640x480 75.0 60.0
     720x400 70.1

Once I have executed one of these workarounds, Fn-F7 cycles through these 2 setups in addition to the ones it does by default.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: unity 5.12-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-24.38-generic 3.2.16
Uname: Linux 3.2.0-24-generic x86_64
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
CompizPlugins: [core,composite,opengl,decor,compiztoolbox,snap,gnomecompat,regex,grid,resize,imgpng,mousepoll,place,move,vpswitch,animation,session,wall,expo,workarounds,unitymtgrabhandles,ezoom,fade,scale,unityshell]
Date: Fri May 25 11:06:42 2012
InstallationMedia: Ubuntu 10.04 "Lucid Lynx" - Release Candidate amd64 (20100419.1)
ProcEnviron:
 PATH=(custom, user)
 LANG=fr_FR.utf8
 SHELL=/bin/zsh
SourcePackage: unity
UpgradeStatus: Upgraded to precise on 2012-05-02 (22 days ago)