old school drop out
I've run an X-type BB on my mountain bike (with Race Face cranks) for a little over 7 years. During that time the bearings froze up once after a particularly wet wide with several deep creek crossings - which is about as long a life as I've gotten out of a typical BB . Other than that it's been problem free. Other than weight and durability a BB is pretty much a BB (with the possible exception of Chris King which allows for replacing the grease). I'd say that the X-Type is good enough that I'd buy one again - probably in the same range as any the upper-end Shimano BBs.