When i first converted, I was at about 75 gear inches if i remember correctly. I changed out my drivetrain maybe a month or two ago, and am now at 69.1", and have been brakeless since the day after i changed the cranks and got clips/straps. I spent the first night learning how to skid, and since i had barely ever used the brake when i had one, I pulled it off and haven't looked back.

My knees feel fine, if not better than they ever have. My father has horrible knees, and i believe I've inherrited them, as I've always had knee issues. Everynow and then if i realize I've done a lot of mashing that day, some of the days that I'll ride around for hours across varying terrain, etc, i'll noticed some fatigue in my knees, but it's not pain, it's just being tired.

I never understood the knee pain problem with cycling, even fixed gear. Cycling is low impact, and once you start building up the muscles involved with the backpeddaling of a fix, I would think that knees should hold up just fine.

Then again, I'm not a doctor.