I think part of the problem with static options is that after everybody had done their initial positioning and blew their encounter powers, the combats themselves would occasionally get static. To put it another way, if nobody's moved, and the situation hasn't drastically changed since your last round, are you going to change your action?
I actually think that the random recharge mechanics, and monsters that did something different when they or their foes were bloodied did a lot more to keep players from just continuing the take the same action round after round than anything.
That and like I said on another forum, responding to Jason's post, most of the PCs seemed to have two types of at-will powers. They had a situational one, and a general purpose one. A good example is the ranger, with Nimble Shot (situational) and Careful Shot (all-purpose) Once the combat got to the point where they wouldn't have to use the situational one, they'd use the general purpose one every round.
I'm not sure what to do about that. Probably when the PCs have a few more powers, especially ones that only kick in when the enemy is bloodied, I'd guess they'd take more varied actions. Like most people here though, I'd have to see and play the full system to know for sure.