Well the bigger issue is that games in general haven't come out that have made it worth it as well as the fact that technology has outpaced games in general.

I remember when FEAR came out and only SLI rigs could really play it maxed out. Then a single G80 crushed it utterly.

Granted though, I run at 2560x1600 and so having a top of the line rig, including multi-GPU will potentially help. But at the same time, seeing how the next generations multi-GPU configs aren't so appetizing (the high TDP's of the GTX280's and the joke SLI boards out there, and potential performance crown issues with ATI + CF) means I'm in a bit of a rut and will certainly wait and see for which rig becomes the best.