I use 6.0. I had 5.0 before and skipped 5.5. As I work mainly for the web it is enough and I am quite happy with the integration of imageready.
I don't think I'll upgrade to v7, since I can do well with my actual one, and I can't afford to spend 1000$ for every new version.
I'll upgrade when Adobe will put an integrated animator in photoshop. It is far too long to work on a mere animated banner with photoshop.