Yes, user-defined categories will probably be added in the next "big" release, which should be out end of august/early september. We first thought, as JHempl suggests, that tags would be enough but obviously many many people prefer to have an explicit concept of category.
About the trial, we quickly modified this morning our trial policy, to satisfy a request from another user: people who have installed a trial more than 60 days ago can use it again (and upgrade to the latest version) for 7 more days. This is simply a quick fix, and we'll think about a better solution.
Originally Posted by sherbs
Any chance you could add user defined Categories under Filters so I could separate my novels, technical books and magazines?
While I'm at it, any chance you could reset the trial periods so that those of us that have trialed before can take another look since all the recent changes?