jennyh :
Well lets look at the 470's negative points.
Hot
Power Hungry
Random game fps, wins some loses some - even to much lower cards like the 5770.
It's Nvidia
Chances of you actually getting one for another month or two are almost nil
Now if we look at the disadvantages of the 5850 toxic.
None of the above
Wow..... Common Jenny atleast pretend to not be biased.
The 5850 2GB wont show a large improvement over the regular 5850 unless you are playing at 2560x1600 or with extremely ridiculous AA. The GTX 470 beats the 5850 pretty handily, coming just shy of the 5870 to be more of a competitor to the 5870 than the 5850. The GTX 470 also overclocks pretty well, not quite as well as ATI, but damn close. However, where it really shines is with heavy tessellation, the major feature of DX11, the Fermi architecture, the same in the GTX 480 and GTX 470, performs a good deal better than ATI making it more future proof.
All this said, it does run pretty hot, but the card's fan never goes very high and is quite quiet so you can combat that to a certain extent to increasing the fan speed. It also consumes a lot of energy, not as bad as the GTX 480, but still worse than the 5870, though not terrible. It wont be readily available for a few weeks, but its not as bad as Jenny makes it look.
As for the random FPS arguement, this is baseless and mostly false. This ties into release drivers. The drivers for these new cards will improve while the drivers of the 5xxx series are fully mature, meaning we should see the GTX 470 neck and neck with the 5870 soon.
You get all this for $70 less than the 5870 and $50 more than the 5850, you need to decide if it is worth it to you.
A good summary:
http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/30321-nvidia-geforce-gtx-470-review-31.html