I got this slot cooler for $10 US ("open box" at Fry's but had obviously never been used) and it's worked well for me. Was getting GPU related crashes in BioShock & 3DMark06 prior to the VCool and haven't had any since putting it in. 3 speeds, nothing to the installation (as long as you have 2 free slots) and it's not too loud even at the top speed.
I don't have good temp info, but I'd say 5C - 15C claimed improvement is about right, and everything runs great now.
I really didn't expect great results and have been amazed that it does what it says. I've never overclocked the 8800GT (625/1800, I think) and don't expect I will because of the heat and my case.
