The cross-linking capabilities seem honestly really cool, and this is something I have often yearned for in managing my own info. I dig that the license is unlimited updates within a major version too. Will give it a shot. :)
Major versions are roughly 18 months to two years apart with at least a 50% discount for the upgrade. I was thinking about a subscription basis but thinking from the point of view of a user, I wouldn't like that myself. I think this is a fair compromise - users get a good deal and I get a little something to replace my flux-capacitor every couple of years.