Collaborative editing

I'm writing a scientific paper at the moment, and I am trying to come up with good ways to do collaborative editing. I am the main author and am doing all the editing myself, but there are several others in my group who write comments. I currently have the source in a Git repository, but I'm really the only one using it.

The way it currently works is that I send out a .pdf of the paper and the rest of the group make comments on it, either by email, or by using the annotation features of Adobe Acrobat reader. Unfortunately acroread doesn't run so well on my Linux machines and its very annoying to try and read the comments. I'd like to come up with a better way of sharing comments. Ideally the comments would be made on the LaTeX source, but that is obviously not the complete document, and there needs to be a way to make comments on the figures as well.

In searching around I've come across this website: http://en.wikibooks.org/wiki/LaTeX/Collaborative_Writing_of_LaTeX_Documents, which I think is quite good, but getting all my colleagues to start using version control systems seems unlikely to happen and isn't really what I want.