Ed Brill is the mouth piece for Lotus and at the latest Admin2008 had a session that explains what to do if some lose cannon in your company wants to move away from Lotus instead of using it to it’s full potential.
Let me give you my two cents about why Lotu is a better choice, they seem to understand collaborative technology way better than Microsoft ever will. Lotus out of the box will allow you to do mail, that is easy but they also allow you to build applications and collaborate.
Most companies fail Lotus and don’t do anything with it but mail. There is also one other problem IBM and Lotus have, they don’t have anyone printing books about how to use Lotus Notes, How to be a Lotus Admin and how to develop real Domino applications for Lotus Notes and the Web.