Works perfectly... IF northern brewer ships you the correct part.

They shipped mine with a 1 1/2" long nipple male 1/2" npt fitting (the right size for coolers, but way too long for kettles). It took me weeks to get it straightened out. And apparently I'm not alone... See forum below for a slew of other complaints:
http://www.homebrewtalk.com/f11/weldless-ball-valve-problems-289321/

Conclusion: I'd recommend buying one of these, just verify that they send you all the right parts for the setup you want (cooler v. kettle).

Cheers!