AnandTech have a pretty solid pair of reviews covering the new GeForce 8600-series additions to NVIDIA's line-up and then a rebuttal to their own review with wider performance comparisons..

The cards are pretty much what you'd expect from a low-mid range product. NVIDIA have made some design decisions that are reminiscent of the GeForce FX 5800 Ultra. Not what everyone remembers it for; the concordesque cooler; but compensating a lack of girth with abundant speed (NVIDIA's design decision for the GeForce FX 5800 called for what was then brand new DDRII memory, but at a limp 128-bit memory interface. Back peddle GeForce FX 5900 exceeded the older brother with slower clocks but a nice wide 256-bit memory interface).

I've nothing more to say so I'll just stop typing.