What to look for with used PowerTap Pro?

I can get a 1 year old power tap pro for under $400. It includes all the hardware, chest strap and is mounted to a 24hole Velocity rim. I have never trained with power before, but it interests me for sure. I would most likely use it just for training because I race with 808’s. If everything is in excellent condition is this a good buy? Whats the reliability on these hubs, its not gonna crap out on me after a few months of riding in the San Diego sunshine is it?