I just checked on newegg. The GTX470 currently sells for around $240 shipped. I say around because of Nvidia's stupid pricing policy. (can't show price until its in the basket, not going through all that on my POS laptop.) The 5850 can be had for $199 shipped. I personally would rather have the $40 and get the 5850.
Thank you Fermi for bringing the price of the 5850 down from $300 to 200. This is why competition is good.
The Zotac GTX470 on Newegg is $235 before a $20 rebate, so $215
Thats a closer call. $15 difference is real close. I think it comes down to Eyefinity vs CUDA. While I love the idea of Eyefinity, I don't have three monitors. CUDA I can use now, either in production apps or games that support PhysX. For $15 I'd probably get the GTX470. (assuming power and heat wasn't an issue.)