I didn't post this on in the Cav arms forum because I want as un-biased of an answer as possible.

How good are the Cav polymer recievers?  Do they have any flexing or breaking/wear issues.  What about mags chewing up the mag well?  Any other cons I am not touching on?

I have one. It is one of the original ones. I know they were coming out with a new model but I haven't kept up to date with it and don't know if it is out yet or not.
I have used mine to some extent. I wouldn't say that I have used it extensively, but I have probably fired over 500 rounds out of it.
I have had no problems with it at all. It doesn't flex, no problems with the mag well. It looks to me like it is very rugged.
The only negative thing I have to say about it is that the stock is far to long.