I'll admit that the project file is a _bit_ less friendly to changes, but we're smart people, we can handle it!
I can not count the number of times someone has come up and asked if i can check in or undo my checkout on some file because they want to make some changes, more often than not one of the project files.
This _never_ happened at my old company. We all presumed that our coworkers were smart enough to be able to merge changes without breaking everything. And you know, the great majority of the time there was no problem whatsoever.