Just about all other decisions depend on having a good idea whether there will be 10 people or 100 people attending. Respond to the forum is you are sure you can be there and let us know if you can volunteer to help, or want to do something like - a demo or discussion or puppet show etc.
We have a registration page set up now. Please regester at:
http://pentaho2008mainz.eventbrite.com/
By the way - I'll be there
-Doug