I agree wholheartedly with this comment. I am in my fifth year of riding fixed, and it is my bike of choice, most of the time. I commute with it (now close to 50 miles round trip), I have done hard hills with it, I have done double-metric centuries on it-- I have done a week-long trip in Colorado with it.

Why do I ride it? because it is fun...

On knees-- if you have the right gear, your knees will actually get stronger riding fixed. It makes your pedal stroke round and helps efficiency. An example-- next time you ride a hill standing up, notice what you do when you sit down... you 'pause'... your legs stop moving, you take a little teeny rest--unless you look for it, you will miss it. That little lag drains your momentum. On the fixie, you sit and keep moving, because you can't coast. That makes you that little bit more efficient on the uphills...and believe it or not, when you go to your geared bike, your muscles are 'trained' to not have that little pause, so you will beat your buddy to the top of the hill--only because of that little pause that you don't have anymore.

I rode almost 9000 miles last year--and 6300 of them were on the fixie. Now for me, the biggest problem with the fixie is that I love to go downhill fast--and that is something you really can't do on a fixie... I have hit 36 MPH on the fixie down hill but that was really waaaay to fast-- I can deal with 28-30 in comfort. Now, on my other bike, I have hit speeds in excess of 50 mph...

If you haven't been on a bike in a long time, a fixie is probably not the way to go, but it is a great addition to anyone's stable. Don't knock it until you have tried it several times...the first time I rode it I had a bit of buyers remorse, but after a few rides, I felt really comfortable-- oh--and I do ride with brakes. I had only one for the longest time, and prior to the trip to Colorado last year, put the rear one on and it has stayed there.

enjoy--

train safe--