I just bought and installed the H80. It was kind of a pain in ass to install due to the stiff tubing. The hardest part was trying to line up the fan+rad while to starting the first screw from the rear of the case. Three or four hands would have been..... handy.
I have it set to the highest fan speed and it seems to be only 1-2 degrees cooler versus the core-contact freezer on average during idle (~29) and under load during a game (~43), and it makes too much noise. The H80 does not seem to dissipate heat as quickly and the CPU's temps rise faster then before. BUT I used the pre-applied thermal crap that was on the block from factory. I'm going to apply some MX-2 and see how much better it gets. I really do hope it gets better!
BTW, the main reason for purchasing the H80 was to make room for more RAM and still have a good CPU cooler. The core-contact freezer is simply a fricken monster and it was blocking one of the RAM slots. I wish I could still be using it actually. It's one of the best air coolers you can get.
- I'll apply the MX-2 tomorrow and chime in again. Getting too late to do it now. Gotta work in the AM.
*EDIT* - Gained another 2 - 3 degrees celcius with MX-2, so total about 4 or 5 overall compared to the core-contact freezer (which was also used with MX-2). Not too shabby. Gonna see if I can squeeze a bit more OC out of this old PII 940 BE, just for the hell of it.