[citation][nom]raider37[/nom]...Crossfire scales way better than SLI anyway....[/citation]
Where'd you come up with that? In the majority of benchmarks, 2xGTX260s in SLI top 2 4870's (1GB) in CF
as seen here. It varies game to game, resolution, options, etc., and 4870 in CF does top the GTX260 SLI in a few, but certainly does not outright win, nor can you deem it to 'scale better'. You can prefer which ever company you choose, but keep opinions out of objective statements, or back them up with hard data.
As far as PhysX, it's a tossup, it has the ability to do some pretty impressive things, and so does Havok. My personal opinion is that a Physics standard API should be agreed upon and incorporated into DirectX (which has been rumored before). This will level the playing field there, and ensure widespread adoption by developers.
In regard to CUDA vs. Stream, I don't know of many Stream apps. Video encoding benefits from Badaboom were the biggest draw to CUDA for me. Until Stream has competition there, it's just not as useful.