4870CF and 4870X2 setups. Also worked on a 9800GX2 setup which was horrendous. Microstuttering was gone on the 4800 series but that wasn't the problem i had. I'm talking room, heat, noise, power as well as software level conflicts; for example, my 4870X2 had an issue with 2D clocking one GPU whilst 3D clocking the other. I don't believe the "future is multi-GPU setups" but they will remain available for those who wish to opt for the extra GPU power.

They count as the 'old school setups' i'm afraid, may only seem like yesterday but we're 2 generations on from that now

The hd5/gtx4 and hd6/gtx5 series are very good in crossfire (the latter generation being fantastic in all aspects). You should never mix two high end cards though for the problems you stated with heat and noise. However, selecting two cards like gtx460's instead of one high end card is a fantastic choice for price/performance and even noise and heat!

nVidia Multi Card Setup = SLI
AMD(ATI) Multi Card Setup = Crossfire

For both SLI and Crossfire goes you need a Powerfull enough CPU and a lot of RAM, and the more VRAM your Videocards have the better as both cards get send the same data packadge and than deside what who is going to render.
So a really bad idea would be to fit 2 cards like for example the GTS250 512MB and GTS250 1GB, because that means 512MB of the 1GB (1024MB) will never get used.

So you can really run crysis on max settings? (whitesnake) how are the framerates?

How would that fare for a Toshiba sat. with Gts 250m?