I just grabbed the Noctua NH-D15 today after almost going for the h110i GT and man does this thing perform well. I just got my 4790k a few days ago and was blown away by the performance of my previous U12S Noctua cooler so getting the D15 was an easy choice and temps are down by almost 20C while running AIDA64 Extreme all while the D15 is running with LNAs. I also disconnected two corsair fans that shipped with my H440 case and replaced them with a single Noctua NFF12 fan from my U12S and I feel it can push as much air into the case while being dead silent. I don't know how Noctua does it but they sure know what they're doing. So, thumps up to Noctua :thumbup:
Its an amazing cooler, got one for my 5930K, temps are really low, and can't hear it at all, even with both fans on.