I noticed that the Visual Studio 2010 module is already included in the beta distribution, and tried it out.

The module installed fine, and it's possible to create Squirrel projects. However, I haven't been able to attch the debugger to the game VM. The game opens up a listen port with script_debugger_attach but the IDE can't see it in the Attach to process... dialog. I guess there is some piece of the puzzle still missing.