I incorporate a lot of fixed gear (spin bike) training, but mostly all interval stuff - 3 days a week. There is no cheating/stopping when youre on one.

I use my fixie in the off season to work on my form and pedal speed. They are also a ton of fun and help break up the monotony of daily training rides.

I'm not a pro. I am Cat3 road racer in Norcal, but I use my fixed gear bike a lot. Using a fixed gear helps a great deal with road racing. The constant pedaling gives you good muscle memory and great response to varying road conditions. I've also notice that I can recover from efforts while still pushing a relatively large gear and that helps in races (for example: the effort to bridge a gap and then recovering at just under that threshold once you cover it). Your body gets used to pushing a larger gear in varying situations. It has helped me with balance and handling as well. I also race at the velodrome here in San Jose, so I might be biased. If you're riding on the road I highly recommend a brake or two on the bike. I know people who ride brake-less, but with cars and that shit is crazy. I also recommend getting a rear wheel with dual-hub (able to mount two different gears, one on each side). Specialized makes a great steel fixed gear for about $700 (called a Langster: http://www.specialized.com/...1101&scname=Road). I ride one...