@binary solo -- yep 3D is quite resource intensive. I believe the main reasons SONY is pushing for 3D games is to learn how to make 3D games for next-gen and because there adding 3D for blu-ray movies anyway.
As for why Microsoft is staying out of 3D -- the 360 doesn't really gain anything from 3D, it can't use HDMI 1.4 and if developers are going to use NATAL which already uses 10-15% of 360's processing power then 3D NATAL games would be pushing the system to its limit very quickly...