After getting my SGS3 less than two weeks ago, there's almost nothing I can say I hate about it. The is one exception to this, and that's the default launcher (TouchWiz).
Apart from having removed wallpaper scrolling as you move through desktops (partly understandable since you can now loop through them) and still having no configuration settings, almost half of the screen is taken up by the dock bar. There's a very small portion containing widgets which the user can configure, and this looks and feels very wrong.
I know this happened because the SGS3 has a much wider / taller screen than the SGS and SGS2, so the difference between height and width is bigger, making it hard to maintain a 4 x 4 desktop grid. I don't see why they couldn't make it a 4 x 5 desktop however, so all this space wouldn't be wasted instead.
Anyway, although TW has some nice features as well (such as a better Apps menu and folder support) I'm clearly not using it due to this. Since I prefer using only open-source software, I'm sticking to ADW launcher, which I've nicely set up with a 4 x 5 widget space (the tall screen allowing this without widgets even getting close to each other vertically). ADW is however pretty old, but I couldn't find any open-source launcher for Android 4.
I'd like to see something based on SGS3's TouchWiz, but with wallpaper scrolling added back and the ability to resize your dock bar (and have 5 widgets in height). A fork of ADW that's still under development would also be nice. Anyone know of a good FOSS launcher other than ADW I could use?