Following the discussion in MEVENIDE-252 I'm adding my +1 towards replacing the synchronizer feature with the IClasspathContainer
As far as i'm concerned, in a maven centric development environment, it makes sense to use the POM as the unique source of project information.
I have been using Eclipse 3.0 / Maven 1.0.2 and MevenIDE 0.3.0 for about a year now, and I have never used the synchronizer feature, I always launch the eclipse goal to regenerate the eclipse descriptors when the POM is modified.
Of course, the best approach would be to choose whether you want to use the synchroniser or the IClasspathContainer so as to please everybody out there 
Lot of discussion on IClasspathContainer stuff in MEVENIDE-252