Training with power has become exponentially more popular over the last 10 years for a few reasons.
  • It has become more well demonstrated that training with power has real, measurable benefits. I'm not going to go into a discussion of all the benefits of power training, but a quick google will give you a good idea
  • Other people are doing it (snowball effect). If you see 3 of your friends with powermeters, you're more likely to get one
  • More interesting to this discussion: the powermeters themselves have gotten much, much better.
I've been lucky enough to afford (at a discount), a Powertap 2.4 SL. Quickly:
  • Wheel is great - gives a pretty consistent power reading
  • Computer sucks. Screen is terrible, etc. I really wish the Garmin Edge 705 supported the 2.4 SL (and now it does!)
  • Needed to use the same wheel/tire in races that you do in training really sucks. I'll be swiching to a CinQo as soon as they come out, I think. I like that you can use the same power meter between different bikes with the PT, but it means you have to either use the same expensive tire in training as racing, or the same cruddy tire in races that you beat up on your training rides.
Unfortunately, the DT Swiss 1.1 rims that the powertap was built into are terrible. Maybe if you weigh 150 lbs or less, but at 170, these need re-truing a fair amount, and have a noticable amount of flex. This really brings out the one big weakness of the powertap system - if you want race data, you have to race on training wheels, and more importantly, training tires (unless you race very seldom or really, really like changing tires).