I have to use "Enhanced GPS" from settings to get reliable GPS lock. YMMV.
I have heard of issues with GB but have to admit that I had none. Running ADW Launcher when I updated and everything was gold upon completion, same with the Wife's DX.
Don't dig it so much though from a theme standpoint (colors and such). While the launch bar is customizable I think I'll be sticking with ADW for it's theme support.
Other than that, no GB problems here (but not rooted and such).