As VMWare Workstation is now free on Linux and Windows, and allows you to create and rollback snapshots. Why not use it even if proprietary?

It's a good question and I'm pretty on the fence about it, and next time I'm reinstalling things I might switch.

I do believe in the whole RMS "respects the user's freedoms" spiel, so all things being equal I prefer FOSS, even if it's worse - but there are limits.

And OSX. Or the functionality is free, but the name of the client might be different