After switching from NVidia (with their proprietary "closed" driver) to Radeon with kernel stock driver I noticed somewhat irritating thing: in XTerm windows, when there is larger amount of text output, much more "flickering" can be noticed, making the output barely readable. Most probably it's somehow related to the way XTerm's windows contents is refreshed; not sure.

It can be especially easy seen during longer compilation, when there are many lines of output scrolled - but it's irritating even during use of text-based programs using ncurses library, like mutt for example, or Slackware's pkgtool.

Well this one can be detected actually by direct comparison - and the best way would be to use slower machine for this, to increase the effect. But when I see the way ncurses-based apps cooperate with your driver, it seems, they mostly 0- after start - first make completely unnecessary refresh of the present XTerm window content, and only then they output their own screen (you can see this when starting mutt, and when using pkgtool). No idea, how this is related to your driver, just I didn't notice such unpleasant effect formerly with NVidia.