For the date, I suggest the date of move be used. It will be a little confusing if there are already follow-ups (as I think Adam was concerned about). Of course, if Q&A becomes fully threaded (that is, where you can see all of the answers and replies to them from one place), then I change my vote to always using the original date as redisplaying the question in Newest Nodes when it has been moved isn't important anymore (to me) since I will have already viewed the thread over in the Q&A section.

...which prompts me to ask... Where do I go to apply to be a Q&A Editor? Now that SOPWifying is so easy, I could just slam those newbie misposts over instead of building up a real pet peave about trying to ban Level 1 monks from posting new categorized questions. (: