In my opinion there's a difference between being "all-powerful" and being capable of any describable action. Something that can manipulate physical reality without limit, but cannot feel fear or remorse, is still all-powerful. I think most people would assume that an all-powerful being would have great or unlimited proficiency with the power, though technically that's an assumption. One could imagine a being capable of eating suns but without the skill to harden a pharaoh's heart, for example.
"Can God create a rock he cannot lift" is still an interesting question, though, for a different reason. It's another way of asking whether God can relinquish any of his power - stop being all-powerful. Ironically, for the answer to be yes, he has to have a certain weakness: He can't have perfect foreknowledge and control of his actions. Otherwise any release of power is simply a choice he has made, and all the consequences are directly by his design.
Even if God had the ability of perfect prescience and gave it up, he still knew every consequence when he made that decision. Everything is still exactly according to his original design - even if he manages to avoid peeking later.
Which is back into the (rather frustrating) free-will discussion, of course. It's just clear to me that, for there to be actual free will, God could never have been completely omnipotent and omniscient. Not that that disproves the Christian God... Frankly, he's portrayed as having a lot of flaws in judgement, not to mention character. It just highlights the impossibility of God being perfect.