(In reply to Aaron B from comment #7)
> I don't have bad rendering during normal renders like you guys, but when
> mousing over the bookmarks bar in chromium the overlayed boxes are usually
> corrupt for me now. R9 270X.

I've had the same issue in chromium with a 280x. (well I haven't tried on
bookmarks, but on any other overlay)
I found a way to get around it, just move the cursor away, and move it back on,
then your overlay should be fine.
I *felt* that this issue came from chromium's new ui library, but truly I never
tested it so maybe it came from gallium3d.
I'll subscribe to this and maybe I'll try building mesa without that commit
later this week.