Cutting the spectrum at nyquist's limit. Not below it. The latter is where the mangled mess comes from.
Whats the point in recording frequencies that have been mangled?What's the point in having an AA filter in the first place, then? Why do all the manufacturers use them on all sub-MF bodies?
Look at files from an E-5 for example...better then the artifacts introduced by raising local contrast back up.
It's a tradeoff, in either case. Medium format cameras could and would benefit from AA filters - but they would suffer as well, too. The Pentax rep spoke to this explicitly.