(Just catching up with this thread.)
I've got 5 users on 2006, and I'm running 2006 and 2007. We've not encountered these problems. The only problem I have encountered is when I edit our .dwt file in '07,... the others cant open it when they start a new drawing file. (even though my 07 is set to save as 04-06). Apparently there is no option to save as a previous release for dwt files. <heads up>
Remember, (IMO) 2007 is still a beta version.
I'll wait for a service pack before I roll it out to everyone else.