Well after telling people for a year that mechanical disc brakes weren't worth the effort I finally broke down and put one on the front of a bike I just built. I've been through a set of 8" Hayes and a set of 6" Hayes hydros. I got SOOOO tired of tweaking the dumb things to get them to stop rubbing that I finally decided to quit discs altogether. I've had Hayes hydros on 3 different bikes, all with some degree of "pain-in-the-buttness". But my Z1 fork only has disc mounts, so...

I got an Avid mechanical and put it on for an honest try. After a couple rides I have to report no rubbing, and very good braking action. Not as good modulation as hydros but I would put them overall about halfway between the performance of V's and hydros. These things are so adjustable it's rediculous. Definately worth a look if you want discs and are low on cash.