Currently looking to make my living space robot friendly, I wonder: can they clean hard to reach spots behind doors or under the ledge of a sofa (I can't remove every obstacle)?
Doors no, couch yes (if it fits). I wouldn’t get one unless you see value in having 80% of your home vacuumed once a day. For me that’s still a huge improvement and spending a few minutes spot vacuuming every two weeks or so is all I need to handle the corner cases.
Robovacs aren't a drop-in replacement for a maid, they aren't a fire and forget cleaning solution for a house that's already dirty and messy or have constant spills and stuff left on the floor, but more for regular maintenance of an orderly place that still gets cleaned or maintained in the tough to reach places every now and then.
But if your place resembles a crack house, a robovac won't magically clean it.