Moire and other aliasing problems can crop up when you least expect it. At least with an MF like the Leaf there are anti moire tools built into Leaf Capture to handle the occasional times this happens.
I nearly blew a very large job because of Moire on the Aptus 75, only Leaf Capture could save these critical images, none of the other suggested solutions worked.
At 33Mp aliasing effects are far less noticable than on the Aptus 22, so I guess, size of pixels is important, maybe the 5D2 will be OK it will be interesting to hear about results further down the line.
I'd say to test thoroughly before a critical shoot, and watch out for the wonderful 'greek patterns', they are impossible to get rid of, unlike regular moire. When I get those patterns it usually means 4 hours in photoshop rebuilding part of the image with a paintbrush. I've even had this on the 1DsII with a very sharp lens like the 90 TS-E, so I guess it is possible with the 5D2 especially if the AA filter is removed.