I did retrofit my commuter/e-bike to disc brakes. I don't have complaints about how they function. They are much better than my cantilever brakes. However, it was expensive. I should have just replaced the front fork with a surly disc trucker fork ($110) rather than have the disc tabs welded on the existing fork. I could have lived with the canti's on the back as the e-bike has regenerative braking... but I haven't got that working again since converting to the disc brakes... but, it's not necessary with the discs on the back as well.

I think I would have plenty of braking power with discs just on the front. I've got them front and back now... but it was a pricey conversion. The extra weight of the the e-bike conversion kit made it necessary. But discs on front would have been adequate and a much cheaper way to go.

When I first installed my front disc brake, it squealed quite a bit. Then I followed the break-in procedure and now it doesn't really squeal at all, at least not when it's dry. Not really sure how it acts in the wet. This was my old bike frame before I moved the parts over to a disc-ready frame:

http://img.photobucket.com/albums/v3...psdzz67ddo.jpg

Oh good! Another chance to post a picture!

I bought this bike with the thought that at some point in the near future, I would install a suspension fork. Well it was more like 8 years later that I found a used one. I didn't have a disk brake so I bought the v-Brake parts and used it that way. It really was less than optimal.

A couple of years later, I found BB-7 NOS on CL for under $40 and a front disk wheel with XT hub for about the same price. I have way too much invested in the front end but it is a sweet set up. Weight wise, it is not much heavier. I used it commuting and found that there was no definitive difference in average MPH between the rigid fork and the suspended fork. I do like the disk brake! The only reason I don't commute with this is the lack of a good fender

[IMG]https://farm3.staticflickr.com/2950/...0664ab98_b.jpgP1020526, on Flickr[/IMG]