Honestly, I don't find CO to require much more button mashing than other MMO's.

I've heard that in earlier betas you had to keep activating your energy building power, but now it's a toggle unless you turn it off. In fact, there is a gameplay setting that lets you make it even less clicky by setting it to never toggle off -- even when you change targets.

The only time you really have to mash the keys is if you're held. That's still a far sight better than DDO where you are constantly clicking the mouse to attack.