I use power meters to train and I do race, but I personally think a lot of non-racers could benefit from power meters if they are enthusiastic about fitness and improvement. Just from a simple level, calorie tracking is far more accurate with a power meter than by using HR or other estimates that are often waaay off. I also think that just having an idea of what one's FTP is and using the power meter as a pacing tool could be helpful for a lot of folks.
I see a lot of people always asking about wheels and such to gain speed, but if people invested in a power meter (cheaper than a lot of wheelsets people look for) and incorporated at least a little structure to riding they'd probably see bigger gains in their riding experience than they would through wheels.