Re: desktop gone wacky... apps fullscreen
First I will say the situation you have is self inflicted,
Explanation:- no packages will install from experimental without you explicitly tell them to,
using the -t option in console, apt-get -t experimental dist-upgrade, Which is a message for a disaster.
Or you have somehow setup the experimental preferences file incorrectly,
At this moment Sid, is stable very stable, just as Sid with Experimental is when setup correctly is. (I run Sid just as I ran Sid with Experimental to pull in 4.7 before it moved but the kde-experimental preferences were setup only to install 4.7 and its dependencies, nothing else.)
Making the assumption you used the experimental repo to install KDE 4.7, 4.7 is in Sid, so you do not need to go anywhere near experimental,
and in the transition from experimental to Sid for KDE 4.7, not more than 10 or 12 additional packages were installed, above the normal upgrades.
Best advice because of the number of upgrades, a clean install of sid, or whatever.