I'm going to make this point, as I feel it needs to be made.
Powermeters are nice. They really are. I have one, and I've only been riding for 2 years. BUT, and this is a big BUT, I don't let it dominate my training plan or my improvement.
I believe, first and foremost, that racer development, from GROUP rides, is being thrown out the window too fast, too soon by too many people. I'm not suggesting that you do nothing but group rides, either. I only make it out to one group ride a week myself. But, there is no way that you can simulate race effort solo, and while a group ride doesn't replicate it 100%, it's far closer than a solo ride.
How often do youpanic when your current wattage drops by 5w at the end of a 20min interval? Not often. Ever dig deeper than you knew you could trying to latch onto the local Pro or Cat1's wheel after taking a mean dig at the front? Often.
So, while I use a powermeter to measure my progress (usually with a 5s, 1min, and 20min test) I am by no means constrained by the numbers that I see on the computer, or my PC when I download the data. A brutal group ride will teach you how to ride in a pack, push yourself to make that wheel, and help you in other ways that a solo ride just can't match.
Ever wonder why us Americans, LA aside, are great time trialists, but never really seem to win anything? Notice that those pesky Belgians aren't always the best TT guys, but they seem to be in it at the finish in every classic of the year? There's a reason for this, and it's rider development, both physical and mental, and it starts with group rides.