@D3: I think that many people are fed up with Nvidia's drivers that only seemed to "magically" improve when DAAMIT's performance started to encroach on their territory. The nerd rage was palpable when Nvidia's 98xx cards turned out to be practically identical to the G92-based 88xx cards only with the support of better drivers.
I would suggest waiting until the 4870 is available at MSRP or below as the 4850 won't be a huge improvement over your 8800GTS 512MB (aside from the driver issue). The single-slot cooler on the 4850 is quite inadequate and the card runs friggin' hot. However, there have been recent deals where the 4850 was so cheap that it could be bought along with a great aftermarket cooler for less than $200. There will also be 4850s and 4870s from DAAMIT's board partners that come already equipped with with non-reference coolers as well as 1GB versions of both cards very soon.
I would also wait until RivaTuner is updated for these cards, as I'm sure it will be soon, in order to see how well they overclock. Since they have identical GPUs, an adequately cooled and overclocked 4850 might end up being the better bargain. If money is no object, then a 4870 or even a 4870X2 will be the way to go.