I know money is a concern mostly for KWA, but I would rather just save double to get the full metal... and the one I want and not settle for the CQB one... if that is the only type of M4 they have out for the sportline...
On the other hand, for people just trying to get into the sport or needing a cheap gun, or a project gun, it's a great gun to start for sure. As people said, the internals is what counts for this product, externals not so much. (still polymer though)