2008 was my first season of racing and my first with a PowerTap. Here are lessons that I learned as a noob power user:
1. Race data will tell you what you need to know. The best you'll be able to do with all the numbers and calculations from test results and training data is an estimate of your FTP. Probably an erroneous estimate at that. This is not a bad thing, as you have to have SOME number as a starting point. But don't put much stock in these premature numbers. You'll be surprised at the power you put out in race situations, when the adrenaline is pumping. My 'best guess' FTP before racing this year was 270w. But after just my second race, I found it was more like 288w. That race was just two weeks after my test results produced the 270 number. A lot of the power data I collected in 2008 was useless. But I learned something from EVERY race file.
2. Use the power meter to improve your weaknesses. Let's say you're not watterrockets and you get dropped in a few races or fast group rides. The resulting power files contain premium data. Focus on the data leading up to you getting dropped and design workouts that reproduce those conditions. DO the workouts.
3. Don't put the cart before the horse. Your abilities define your power output, not the other way around. Don't fall victim to the numbers, especially in races. "Oh no, I'm producing 350w, I'd better back off." I started racing much better after I started covering the PT computer with a piece of blue painters tape (leaves no residue) during races.
4. Using the power meter effectively WILL produce results. My FTP was around 315w at the end of race season (up from 288 at the beginning), and I owe the improvement to interval after interval after interval with my PT.