jchabalk 

i had a similar experience to yours with the avid mechanical disc brakes.

My mountain bike with V-Brakes still has the best stopping power when compared with my mechanical disc equipped bike and my canti equipped bike. Hands down, no questions asked. (the bike with cantis probably out-performs the bike with discs too)

In dry conditions.

The thing about the discs is that even when they're soaking wet the stopping power is pretty much identical to when they're dry where as with V-Brake and Cantis I lose a significant amount of power when they're wet.

I wouldn't say I'm necessarily sold on the mechanical discs and if i had a mulligan on the decision to buy my frame with disc tabs instead of canti studs i can't say i would make the same decision but the mechanical discs do work pretty well in all weather and the others not so much.

EDIT: My Disc brakes are the BB7 Road with Road pull brakes. That bike and my canti equipped bike both have the same 700c tire on them and a similar rim. Both are built up in a pretty similar fashion too