It depends on the games you play.
Like teh boxer mentioned it'll be the most benefit in recent and future games that are shader heavy. Also turn on features you could before, like FP16 HDR+AA, DX10, etc.
Older games you would just be able to crank the AA and such like BF2 mentions, and maybe boost your min fps so you never see slowdowns.
Anywhoo, mainly depends on the games, some are worth it, others would benefit more from you spending money on a bigger monitor because they wouldn't need much power.