-- why are you bothering reading a 3 year old review?
-- you should be asking your coach what measurement tools you need, since you have a coach
-- if you are not interested in reviewing your power data after the fact, and your coach isn't asking you to get a power meter in order to review the data or to train at specific wattages, you do not need a power meter. If you want one, fine, but you don't need one, so stop whinging about how much they cost, that is how much they cost
-- you can rent a powertap wheel and head unit if you want to try it out and measure your e-wang

(edit, yeah, I'm grumpy right now. deal with it.)