I guess I don't see the problems with licensing/moving that others mention below. The original registration email I got included all the information needed to move the license, *even* when the original system was unavailable. Yeah, it was slightly annoying, but only slightly (you have to use the license number and the admin key included in the email to *unregister* first, then register the normal way).

Anyway, it's a pretty good app, but with some quirkiness where the address book entry is created, but WP gives an obscure error. Could be better, but there isn't anything else like it (that I know about, anyway).