After installing gnome shell, without any problem, after log in the fonts are missing and it looks like crap...nothing is readable.
Don't want to make it a double post, because my issue is similar to the one from this question but for me the problems have not been solved properly. After running the commands from that post, and installing the latest AMD 11.10 driver, the Gnome shell display issues have been solved. But each time I move the mouse in the upper left corner, to bring up the applications...my entire screen flickers. Without the applications been displayed, everything looks fine.
Hardware: ATI HD4870, Intel Q6600.
The last AMD drivers (11.10) still has problems like screen flicker but you can reduce the screen flicker active the Desktop Free of Fragmentation in the Catalysm but may cause other errors and the system feels slower, to run Gnome-shell without problems install the open source drivers. check this ATI - Ubuntu Oneiric Installation Guide, install/unistall/remove, etc... open source drivers or privative drivers
This didn't completely fix the issue for me, but it made a significant improvement. I have a Radeon HD 5770 in my desktop connected to a 24" Acer Monitor via DVI, so YMMV.
Varying the "Graphics processor scaling" didn't seem to make a difference, but the transition to the Activities view is considerably cleaner, if not perfect.
Hope that helps a bit until we can get a permanent, real fix!
In my case I am using an Asus laptop with Radeon HD 6470M I enabled the Tear Free Desktop under Display options within the catalyst control center and it fixed the problem.
i have tried all the possible tweaks to overcome this problem , actually it is not the problem with gnome 3 it is the problem but with the ati drivers by the company , so plz do not install any driver after installing gnome-shell , open drivers works very fine....even when u r having both unity and gnome-shell.
New Catalyst driver (version 12.1 - 01.25.2012), Gnome shell now work!!! (I'm in test), chek this guide to install or update - ATI - Ubuntu Oneiric Installation Guide