I have finally worked through the issues to upgrade our fairly large database from 0.67 to 0.7.854 e.g. no version number on the older databases so gives null exception, duplicate mail addresses, demands a real username field for all users. The new version seems to have a number of very useful improvements e.g. alphabetic sorting of projects, my issues feature across all projects, the ability to fold projects in the project view (Not sure that this folding is remembered long term though), the count of items like attachments in the bug details view etc.
The only downside from our perspective was that the upgrade lost some of our per project security roles, which is not a great hardship. We also use Windows authentication and so the user names are of the form <domainname>/username. The downside now is that a lot of the project based functions display using the user names rather than the display names as they used to. This means that we see the less user friendly <domainname>/username form a lot now. This is not a show stopper but does make it less user friendly.