Bought it and wasn't a backer. I played some of Planescape but never the whole way through.
What struck me with Torment right off the bat was how it reminded me of Roadside Picnic. The book, which inspired both Stalker and S.T.A.L.K.E.R., has this focus on interacting with the unknown. Items in the zone has value for research, but the harm, gain, or inertness of alien objects can't be determined or forseen. The first areas of Torment gave me the same unfamiliar vibes, though from a different angle as you're interacting with ancient forgotten technology or magic.
I'm really looking forward to playing through all of it.