Stallman may be a caricature of what he stands for but he isn't dumb.
The main contention with Mono is not that MS only has an agreement not-to-sue with Novel. Customer of Novell are OK, others are not, which raises the question of what are you really getting yourself into if you create an application using mono that can be installed on non-Novell platforms like Ubuntu for instance.
With WPF and Silverlight, there is a real possibility that .Net can push the boundaries of Windows and get installed on Linux and Macs. That may not represent the wishes of Microsoft for a Windows-only world, but I believe that this shortsightedness is very limiting to the development of .Net, and by extension also limits what software companies can offer to their own Customers.
I really wish MS made it clear that it will not punish customers who invest in .Net and want their application to work on multiple platforms.
EDIT: just found and read this excellent article and I must say it puts a lot of the misinformation about mono in perspective:
Why mono doesn't suck., I only wish there were more links to resources to justify some of the positions but it's a worthy read.