Waste of money and an inferior product....
When it comes to multi-GPU setups you will find that Nvidia's 3-Way SLI is still the faster product and with 8800 GTX's on the market for £200.00-£230.00 it's now possible to build a system with Quad core, 780i SLI, 3 x 8800 gtx and 4-8gb RAM + 24" HDCP LCD for less than 1,500.
Benchmark wise 3-way GTX is faster than 4 x 3870's or 2 x 3870 x2 (and 3-Way 8800 Ultra is king.) in ACTUAL GAMES (CRYSIS, HL2:EP2 etc) although ATI have had the edge in synthetic benchmarks for a while now (ie 3DMARK '06) but they're ultimately meaningless in the real world.
I can understand that you might pay this amount of money out if you lack the expertise to build a system with this spec (the only hazard being watercooling.) but surely the majority of hardware junkies and gamers will just build their own systems and save themselves thousands for the sake of missing out on a tacky case.