I have a Spikes upper that has been excellent. Mine has somewhere around 4500 rounds through it and runs perfectly. Mine is a 16" though. I wanted to try one for the good pricing and many good reviews and so far mine has lived up to it.
I do have a 14.5" but it's a Colt. I like it a lot. I didn't think the shorter barrel would make that much difference but I really like the shorter barrel now. Mine is light and well balanced. The only downside I've found can be easily corrected. The downside is in swapping parts. The perm attached FH makes it a little more difficult to swap out stuff like a ff tube. So a person should just make sure they pick the fh and tube they want in the first place and then no problem. Of course things can still be swapped later, just not as easily.