Upgrade to Contribute 4 ??

I am the primary editor for our department's website ( www.isp.state.id.us ) and most of the work is done by myself and a few others in our department with Contribute 3. It's getting the job done for us and I'm a firm believer in the "if it ain't broke, don't break it" school of thought. However, if a new version of software will bring enhancements and the bugs have been worked out, I'll give it some thought. Tell me why I would (or wouldn't) want to upgrade to Contribute version 4.

Also... if I as the administrator upgrade, do my other users have to as well or could they stick with the versions they have?