Here's my experience thus far ... the system: Asus P5B-E, E6400 (not oc'd, yet), 2gb Patriot DDR2 800 (PC2 6400) ... etc. etc. in an Antec Performance II case... was running idle around 42-45c with the stock cooler and AS5. Now, on to the Infinity... the fit is tight no matter how you cut it! All temps noted were pulled using SpeedFan...
~ Initially I was going to mount this with the wide side running north / south... thus you'd have the fan on the interior side of the HS blow out toward the back of the case. Clearances looked good for the P5B-E until I added the clips with the push pins.... The caps to the left of the socket, toward the case backside, are in the way ... touching and possible crunch factor when push-pinning! So, mounting with wide side running east / west is the only option for this setup.
~ All's good but trying to push those pins in a built system can be a bit tricky! Aluminum fins are sharp too, but a little blood never hurt anyone! ;-) So push-pins done and fan mounted, have it blowing north, toward the PS... so might help suck some heat from the Evga 7900GTX that's just a bit below the fan... just using the stock fan that came with it for the moment. Seems to run quiet...
~ And now to put the power to it! Idle temp looks to be about 32-35c, excellent... PCMark06 runs it up to close to 50c with a 5922 score... Running Orthos now for the last 35 minutes and max temp has been 52c. And that should get better once the AS5 cures a bit...
Just my 2 cents...
ps: The weight isn't really too bad, I've used heavier and this seems to be a pretty solid mount....