When I got my first fixed gear (a conversion) I left the brake on and loved it. I rode for 6 months and practiced not using my brakes, skidding, skipping, etc. Then i eventually I got good enough and bought a entry level track bike. I removed the brake and I did fine. I got better and better. 6 months later I pretty much mastered riding brakeless (well, at least I felt that way). But here is what I noticed about me riding brakeless:

1) I had to keep my gear ratio lower for control and skidding. This resulted in slower riding.
2) I had to ride generally slower for safety reasons - I could never all-out-sprint in traffic.
3) I had to pay attention to every car's potential move and anticipate everything far in advance.
4) I had to begin my slowing down on hills sometimes a full block before the bottom.
5) In general I didnt enjoy biking as much. I missed going fast.

I hated going so slow. Then after getting murdered in my 2nd race I decided to change everything on just one bike. I put a brake on again and increased that bike's gear ratio. Wow, it was fun to ride fast again. I could now wait until the last second to brake and I could ride at any speed. Thats the part i missed the most. I like to ride at 48x15 or even 48x14 in traffic. Now i have brakes on both my bikes.

I don't admire brakeless bikes anymore. When i see a brakeless bike I see people who are chained to riding with restrictions. I feel a brake allows you to do whatever kind of riding at whatever speeds you like. Thats just my opinion.