My issues:
As I found with 10.6, the text on the ATI registration window that pops up at the start is corrupt. Abiword is the only word processing software I have installed, I don't know if that is relevant.
I increased the scan slightly in CCC to minimize a small black border. No problems, but when I restarted the desktop was now so overscanned that it had moved slightly beyond the frame of the tv, cutting off the date and portions of icons. I clicked on CCC and without having to do anything else, the issue fixed itself and the desktop returned to the correct resolution. This issue occured each time I restarted.
I tried Metro 2033 and the three Company of Heroes titles: all ran perfectly. However, the two Dawn of War II titles crashed after the opening cinematics, just before the main menu appears. All games were played via Steam; I say this just in case the extremely recent inclusion of the ATI drivers on this platform could be causing me problems.
I restarted a number of times and none of the issues fixed themselves before finally deciding to reinstall 10.4, the drivers I had been using without issue up to this point: once again all issues were immediately resolved.
Any ideas what could be going on here? Why does my rig like 10.4 so much? I am more or less at the stage of sticking with 10.4 and ignoring all future drivers: that wouldn't be the end of the world, but it would be nice to know that I could move beyond 10.4 if I so desired. Any constructive input would be much appreciated.