Thought I'd put in a good word for Solidwork's built-in collaborative tools.
We recently completed a project with 4 designers working simultaneously on the one product, taking advantage of Solidworks' ability to get/release write access to parts.
We needed to do a little extra set up to make it work (turn on collaborative options, drag collaboration icons onto the standard toolbar etc), and we needed to call each other frequently to say "can I have write access to part x, which you have open".
We also did a couple of other things to make multi-user work less complex, ie. we had one part containing central geometry such as common axes etc that we would insert into the top of the feature tree of most parts. Furthermore, most parts had a common "assembly origin" (much the same as if you're designing a tail light, the part origin is usually on the firewall of the car).
I liked the ability to reload changed parts as others were working, and see their assemblies evolving alongside mine. I also like the ability to hot-swap, meaning swapping parts with another designer to solve a tricky area/detail, then swapping back to continue development.
There are all sorts of caveats, but the end result was a very rapid, stable development. Sadly I think that ProE is far ahead of Solidworks in this area, but there is still potential for creative Solidworks users to achieve the same end goal - a collaborative project.
A quick word on network vs local part editing. We have a fast network. It works. To be honest the slowest thing about working on Solidworks models is the tiresome rebuilds.
Regards,
Anthony