From what I've heard, the transitions between loops seem pretty decent. The trick is that they are cued up to play on the 'one', so how well they transition will be a function of how well you set the loop boundaries.

But bottom line is that anything you are playing or doing will tend to mask what goes on at the loop boundary, and I doubt anything untoward is going to go on, because a loop that hiccups or drops out at transitions would be no more useful on drum loops as it would on whole mixes.

The main issue comes from a song segment transitioning to some point other than it's normal destination. Naturally, this is going to depend on how varied the segments are. But if you loop a solo section, then have it come back to where it normally continues from, I don't see much cause for alarm, Dennis.