Just an uninspired game with no substance
The truth is, CO is rather uninspired and gets old quick. Sure, tinkering your very own hero is cool and the action combat is cool too. For a while. In the end you will always attack with the same 1 or 2 attacks anyway, and around level 16 you pretty much have all you need.
The game has little interesting to see or do despite 2-5 minutes lasting "kill x of z" missions. With no classes and mishmash of powers teaming up and cooperating is not really possible.
The fact that Cryptic is still massively nerfing powers even after launch shows they have no real concept of their game and work on it on the fly. Meaning the game is practically in constant, paid beta. I found it quite a letdown. Sure, its fun for a few weeks, but after then it gets repetitive and boring. Nothing really new and exciting to see.