But any functionality differences besides the CCD resolution?

See, here's my thinking. I don't care about the extra rez, I'd be most likely at 1600x1200 for most of the shots anyway. And that's lower than the lowest rez of the SD200. So if there's no other difference, then I'd want the cheapest of the three cameras.

I just don't want to buy one and then kick myself for giving up some other feature. Like, the continuous unlimited movie clips that you get on the SD300.