Had a short ride yesterday with my little brother (who managed to keep up on an old mountain bike) to test out some Tektro mini-V brakes. Overall I'm impressed with how they feel compared to the Avids shortys that came on my Supernova. Braking power feels substantially improved, it's not a night and day difference but I can definitely notice it (btw, I kept the same brake pads that came w/the avids). My initial concerns about not being able to modulate the brakes as well due to the increased mechanical advantage of the v-brakes plus not using travel agents were unfounded. It definitely stops quicker and easier than the cantis but there is still plenty of room to gradually apply brake force.
The one drawback with the v's is the clearance between the pads and the rims. There is about half as much clearance now compared to the canti's. This doesn't bother me as I ride mostly on the road these days but for those requiring mud-shedding abilities I would not recommend this setup without travel agents.
Now, one question I'm sure some of you might ask is why did I want to go through the trouble of switching from cantis to vbrakes? The answer is that my EC90x carbon fork was juddering violently under heavy braking. After some analysis, I determined the cause to be the canti design coupled with a slightly flexible carbon fork.
What happens is when the front brake is applied, the fork needs to resist the backward force from the wheel. If the fork flexes backward even slightly, this will cause a tiny increase in the distance between the brake pivot bolts and the cable hanger up above -- causing a sudden increase in the brake pressure. When the fork reaches its flex limit this pressure is relieved and the fork will 'snap' forward and the process starts all over again. This happens in fractions of a second and was causing my severe 'juddering' problem.
Since v-brakes are mounted entirely on the fork itself (ie- they don't rely on a fixed upper cable hanger), I reasoned that they would solve this problem and indeed I'm happy to report there is absolutely zero judder now with the v-brakes even though I am using the same pads.
The Tektro's I purchased are the 80mm ones found here: http://www.tektro.com/02products/14926al.php
I got mine brand new for about 25 bucks on ebay.
(standard disclaimer: I am not in any way associated with Tektro or its affiliates other than being a happy customer)