There was a launch-day patch, which either 'balanced' or 'nerfed' powers. Which word you choose will depend a whole lot on whether you were affected by it. Mostly this hit the pre-order customers, who had gotten early-access to the game prior to launch day. For those of us starting just after the patch, there doesn't seem to be a lot of impact yet.
Instances (Champions Online operates as if it is a single server with a variable number of instances of each zone) were busy enough, but not too busy. By comparison, closed and open betas were a whole lot busier. There were still a few issues now and again where a zone change or instance change would take a quite a while, leaving you wondering if you'd actually hit the key or not. Then you'd realize that it was just being slow again, and resign yourself to waiting a couple minutes before the system caught up.
Queuing for spawnable mission targets in the field was much reduced, and it looks like many of those missions have more of them than they had at beta, which is good. Not much makes you feel less super than standing in a queue waiting for a wounded soldier to respawn so that you can zap him with a medical kit or queuing for a target villain, especially when there's six or seven groups of you waiting your turn.
All in all, it's a fairly solid experience, unless you were an early-access hero and Doctor Developer's minions hit you with the immitigable nerf gun on launch day, or got hit by the emergency server maintenance just after midnight the following morning.