@b0rk backups and restore testing is a very big one - lots of backup software is easy to set up but awful to recover with. By that point they've already hooked you, they have little incentive to do much but take your rent money until you have a problem, because nobody wipes their main PC to test it.
I use it for new OS testing and sometimes trying things out for friends - resizing positions is a crapshoot much of the time, and a problematic install can hose the whole system, so yeah. Paranoia.
@groxx thank you!