With regards to multiple check-out nothing new is added in 5.0. VSS in 4.0 already supports this, if you enable it in the VSS Admin tool. The way it works is that the version control backend will automatically attempt to merge the files. In most cases it succeeds
and both check-ins succeed. In cases where the exact same lines has been modified the last check-in is rejected. The developer then has to resolve the conflict manually, and check-in again.
Keeping track of versions across installation can be difficult. Even more so if you use XPO files as a way of deploying. I strongly recommend only using AOD files. In combination with a VCS it requires a build step. In the next update of the documentation on
MSDN we will release a documentation on how to setup an automated build procedure. Using an AOD file you can stamp each version with a build number, and you can label (VSS term) your VCS files with the build number. Then you know what you got at all times,
in every environment.
Regarding IDs, *sigh*, we know. What I can promise is we will address this in the very near future after 5.0. If we don't Microsoft will be out-of-IDs very shortly. If the solution will be GUID based or not is still not decided. The other obvious alternative
is NAME based - like .NET and C#.