I'm a dork and I like me some power meter. I used a Powertap forever, and they are great and they work really well but when you're me you have to ride our wheels as customers are likely to ride them, which also means you can't be tied down to one wheel. So I have a Quarq, which means that this year is the first year in which I've done all my (road) races with a power meter.
Now, I'd tell you that I'm pretty diligent at training, I can push myself pretty hard and I very very rarely skip workouts and my training is exceptionally well planned (I outsource that part), so the work that I do in training is really representative of my physiological capacities. Except it isn't. I just did the 5th anniversary edition of the greatest race ever invented (which our team co-promoted). This is a hard race, with one steep steep climb that lasts maybe 3 minutes, and then a longer one that starts off not so bad but just strangles you at the end with about a 20% kick that "levels out" to around 15%.
This was the first time I've ever raced with a power meter on a course that hard, and boy am I slacking in training. My normalized power for the whole 110 minutes of the race was about what I would have told you I could do for an hour, and I just smashed most of my sub 10 minute marks. I beat my prior 5 minute mark on more than one lap, and I have to go through it again to see, but I think I broke my 4 minute mark twice in one lap.
Not everyone out there who rides wants to go faster, or learn where their limits are, but I suspect if you're reading this that you're at least curious about how fast you can go. Training with power is an effective way to track and quantify your training, but if you REALLY want to push yourself, there's nothing like racing to get you moving.
The sad end note to this tale is that I missed the 3 man break, didn't win the race, and in fact after I did my best Richie Porte to keep the 6 man chase group strung out for Paul (if our chase got to the finish hill in one piece, he was super likely to take the group - which happened), I drifted off the chase group and finished alone a few seconds after them.