I've been using it ever since. It stores data in plain text files (dokuwiki markup) and in addition the folder structure is mirrored in the note hierarchy. Zim is open, cross-platform, can include Latex-formula, and is extendable with plugins written in Python. I really also like that it is a proper desktop application instead of some webapp that changes UX every now and then, usually to worse, and that is dependent on network connection. After learning the keyboard shortcuts it is really a pleasure to use. Five stars * * * * *
I keep my Zim notebooks (separate NB's for Work and Personal things) in Dropbox for easy syncing between two desktops. Other Win7 and other Ubuntu.
edit: Added mention to Latex, as it might be of interest in this crowd.