Pros: Great undervolting, lots of airflow, and great static pressure.
Cons: Non-standard 5 pin connector. Not really a con but it's worth mentioning that this is loud at full speed. Of course what do you expect at 3900 rpm?
I don't control it with PWM and it still is very silent. No ticking or anything at low voltage like in many high performance fans.
I have this on my Megahalems and it is awesome. Upgraded from a Panaflo and temps went down several degrees (I don't remember the exact numbers). The nice thing is I don't even turn it up anymore since I get good temps even at low rpm. When I do turn it up I only turn it up a little since I don't want to kill the R4 in the back of my case .
The lesson is, always check old dells for fans. Dell usually puts really good fans in their computers .