Originally Posted by
valygrl
Get the book Training and Racing with Power Meter by Coggan and Allen. Read it. If you still want a power meter after that, and you are ready to either buy or build yourself a training plan and follow it, then go ahead and get a PM.
Plus a gazillion. A power meter is a great tool, but like any tool it only works if you use it properly.
Used as a part of a structured training plan, the power meter will help you get faster.
But following such a plan is not everyone's cup of tea, as Silvercivic points out. The Book will help you get a feel for that.
As for whether a power meter is helpful without a coach, the book will also help there. To get the most out of a power meter, you need to track and analyze your data, and adjust the training plan accordingly. You can do this yourself, or you can pay a coach to do it.
Reading the book will give you a feel for whether playing with all the various metrics (TSS, CTL, ATL, FTP, etc.) is fun for you or a chore. If you enjoy it, and put in the effort, you can get a lot out of your power data yourself. If you don't want to spend time analyzing all that crap, then you need a coach, or just skip the power meter all together.