There's no point in brand loyalty when it comes to PC components.
I concur - I have switched from NVidia to ATI depending on what I required vs budget at the time.
MX440 -> GFX5700LE [which got a 80% overclock on stock cooling, blinding!] -> X1650Pro -> HD4850.
Only other consideration I have had is Linux compatibilty, ATI used to be a bit shaky but the current FGRLX or whatever it's called is not bad, VSync issues aside.
The £150 XFX 4890 [click me:
http://www.overclockers.co.uk/showproduct.php?prodid=GX-124-XF] is
astounding in terms of price/performance, and if my 4850 [currently on the site for under £90 - clicky:
http://www.overclockers.co.uk/showproduct.php?prodid=GX-127-XF ] is anything to go by, it will handle pretty much everything at 1080p.
FWIW IIRC my 4850 does Crysis Warhead everything maxed unless otherwise stated] at about 20FPS [perfectly playable] in 1080p without AA, which I don't need, personally, at that resolution. 720p with AA is better overall, and means I can play windowed and keep tabs on my servers at work while 'working from home'
4890 should wee all over that, happily.
In fact, the only reason to go for Nvidia over ATI at the moment is if you
really need PhysX hardware acceleration [hint - you
really don't] or if you are doing CUDA work [which I very much doubt].
Be interesting to see NVidias response to the 5000 series.
