I am issued a Colt every day. My SCAR's are much better fighting rifles in every way that matters to me. It takes longer to get hot and dirty, stays reliable longer, has an adjustment for use with a suppressor so it doesn't beat itself to death while running one, and has a folding stock. It is also mil-spec, so the parts interchange comments above make no sense to me.
Downside is cost, but it seems reasonable that better guns cost more.. I will admit that I don't like the reciprocating charging handle, but I don't like the AR15 charging handle either. Just use a vertical grip or MagPul AFG and it doesn't matter.