If R600 has very similar specs, but requires less power to juice the beast up, I'll go with them. Also, if ATi still maintain better overall image quality, like it is right now, I will go with them, since I always prefered Anisotropic-Filtering over Anti-Aliasing, especially if they keep, and even "upgrade" their less/non angle-dependent A-F technology (HQ A-F) in R600.
Honestly I am very excited about the G80 specs, but I won't do anything impulsive. I will wait until both G80 and R600 are put on a table and get compared between each others, and not just benchmarks, but architecture comparisons, technology advantages, and such.
Patience is always a virtue, especially in the GPU/CPU domain.