The S-FLEX's are by far the absolute best fans I've ever used, period. I love em. I've now used all of the different flavors, 800 RPM (100% silent), 1200 RPM (damn near silent), 1600 RPM (very quiet and good amount of airflow).
The Crystalfontz display is wicked sick, too bad I still haven't gotten around to setting it back up
And the case, oh wow, the case. Best LiLi ever perhaps? I dunno, but I sure love it. The layout is the dogs dangles for sure, and plenty of room to spare for everything. Also dual PSU capable and pre-designed for watercooling. They did an excellent job to say the least. The only case I'd rather have besides this one from LiLi would be the LiLi Cube case which is totally secks, but at $350ish it's a bit too pricey for me.
They are spensive, no doubt about it, but I think they're quite possibly the best fans you can buy. I love the hell out of em. I wish they made a higher CFM S-FLEX, for my new exhaust fan I was forced to go with a Pana.