Yeah- the 460 is considerably faster. @ 1680 x 1050 it trades blows with my SLi'd 8800GTXs. I was going to get one cause they're so cheap and perform so well- but recently got a 24" monitor and @ 1920 x 1200 I'm wondering if it'd be wiser to just go with the 5850.
Anyhow, if you're gaming on a single 8800GTX @ 1920 x 1200 then the 460 is gonna' feel night and day different I'd imagine.
Go for it.