Shifting while not going straight

[SoftwareBug2.0]

I have a couple related questions:

1) How much of a problem is it to shift in the middle of a turn? I know that at least some teams write their code so that if shifting won't happen if you're in a tight enough turn.

2) Has anyone built a shifting mecanum, rather than an octocanum? I've seen a design, here: http://www.chiefdelphi.com/media/photos/38068. I'd be interested in knowing what the shifting logic was and why. I'd especially be interested in knowing whether or not it's allowed when moving in directions other than straight ahead.