I'm looking for a way to put several of my projects under version control, with the least amount of filesystem-level obtrusiveness.
The rationale for this is because my dev environment is mostly FS-based (total commander + notepad++ + wing + scripting tools with python), so FS changes (including, and most annoyingly the .svn directory of subversion) hurts .
My version control requirements are very basic: commit/rollback/browse ,and good utility support.
Which one would you recommend?
Bazaar has just a .bzr directory at the top level. It also works on all platforms natively (Git is still somewhat hokey on Windows). I find it simpler than Git too.
Community wiki so others can add more info about Bazaar.
These guides should help you get started with bazaar:
Mercurial, git and Bazaar all just put a single directory at the root of the project. All of them are plenty powerful enough to handle the requirements you listed.
Mercurial and Bazaar are written in Python, and you mentioned you use Python for scripting, so picking one of them could be an advantage if you ever want to look at how they work or write scripts that use them.
EDIT: Here's some more information on writing Mercurial hooks in Python.
Mercurial only uses a .hg directory in the top top directory and it has TortoiseHg that makes it easy to use in Windows.