Nabil,
I've composed a follow-up email that I send to users when I add them. It was necessitated by the fact that Adobe's invite usually winds up in our Postini spam filter (an Akimai issue) but has grown to include answers to the user's most common questions and links to relevant Adobe help pages. I can post or send you a copy if you would find it useful.
I would love to see Adobe let us customize the invite. That was something Kivuto let us do with their OnTheHub.com distribution system.