Pros: low heat levels,
When I built my current rig I had my Zalman CNPS11x on top of my i5 3570k. However the thing was huge and was not cooling the 3570k as it cooled my previous 2500k so I decided to retire it and get a popular Corsair water cooling solution.
The H80 is extremely easy to mount. My Zalman CNPS11x required 2 people and lots of time to mount it on the CPU however the H80 was almost as easy as the stock Intel fans that comes with the CPUs. When I installed it, i immediately noticed 10-15 degrees of difference, even more at times compared to my Zalman CNPS11x, which is also a good air cooling unit. I am to this date extremely happy with the cooling of my CPU. I currently have my 3570k OCed at 4.2 and the highest I see is 70 degrees. When my Zalman CNPS11x was installed I could see as high as 90 degrees while gaming. The 70 degrees might sound high for many of you, but please keep in mind that my room is extremely hot and humid in the summer. When my ambient temperatures become normal, or close to normal, I am sure I will see lower temperature levels.
The only downside of the cooler are the fans. They are GREAT fans, thats a given but at medium or high speed they are extremely loud. Some people may get by the loud noise and dont mind it, but for me that was a huge problem. I replaced the stock fans with Noctua fans and even at high speed the Noctua fans are quieter than the H80 stock fans on low speed. The only downside was that my temperatures rised 4-5 degrees but that is ok. Perhaps there are fans out there that will cool the radiator as much as the stock H80 fans and sound as low as the Noctua Fans. If there are, do not hesitate and buy those fans and replace the stock H80 Fans.
The only reason I gave this cooler 4 stars is the noise. Other than that I can not find a single thing wrong with it. I just hope that it does not leak on me :)