Semi-maximised windows' button/indicator are confusing

Semi-maximised windows show the same last button/indicator than normal windows: a square that is supposed to mean "click to maximise".
In fact, clicking that button in semi-maximised state brings the window back to its "restored" state.

This is confusing for the user.

This should be fixed by either:
- Keeping the button as it is but changing the effect to maximising the window; or
- Keeping the effect as it is, but changing the button so it resembles the one that a maximised window shows (a rectangle instead of a square)

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: unity 6.12.0-0ubuntu0.2
ProcVersionSignature: Ubuntu 3.5.0-22.34-generic 3.5.7.2
Uname: Linux 3.5.0-22-generic i686
ApportVersion: 2.6.1-0ubuntu9
Architecture: i386
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
Date: Mon Jan 14 14:58:24 2013
InstallationDate: Installed on 2012-10-21 (84 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release i386 (20121017.2)
MarkForUpload: True
ProcEnviron:
 LANGUAGE=en_AU:en
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)