Jim, the reason the "unfiltered" sensor version costs more is that it is the same sensor with an additional layer added to offset/negate the AA filter. one more layer = more cost.
I don't know whether we'd be able to see a difference. I think the better question to ask yourself is whether the subject matter you usually shoot contains things that would frequently result in moire.
Thanks for that clarification, Tim.
You are right, rarely do I shoot something that results in moire, thought there have definitely been a few times it has happened, and it is annoying. I see it more with our P&S, or my cell phone, with shiny fabrics, window screens, etc, than I do when using my 5D II, though I imagine then it maybe has this low-pass filter on it.
Why does it seem there is never one right answer. 



