I think it's worth putting emphasis on the fact the hibernate synch always you to develop (from the hibernate site) from the middle out, ie. from the .hbm.xml files to java, and also from the back forward, ie. create the schema -> hbm.xml -> java, same as middlegen. Personally, I prefer the back-> front approach and I've been using the plugin that way for a couple of months now.
I would also have liked to have seen a description of the custom templating functionality that can take the class(es) from the hibernate model and pass them into a velocity context to allow you to automatically create additional files such as JSP forms etc.
Congrats to Joe Hudson on the development of this project, it really has saved me a lot of time, with a bit of polishing of the documentation (mainly to reflect the very active and rapid development) I'd be happy to pay to use it in our team.
Keep up the good work,