Thumbstick control, or equivalent on a trackpad, is entirely out, as far as I am concerned; I am not interested in remote-steering a motorised wheelie bin with a camera on top.
Note that I am not saying teleportation is the only option to it, nor would I ever try to take it away from anybody; You do you.
I want smooth motion too, but it has to be smooth motion that feels at least halfway natural, and has a decent level of connection to your body.
As previously mentioned in this thread, I favour well implemented walking in place (with foot tracking, etc), as a complement to room-scale free moving about (basically replacing the teleportation element, in currently common context), but the least I could accept, would be simply pointing at a spot on the ground and holding down a button, to walk in that direction, with your velocity being determined by how far away from yourself you point. (EDIT: Hold your aim on one spot, while approaching it, and you will inherently slow down and come to a stop in a semi-natural manner)
As for omnidirectional treadmills; I'd love a good one! ...but the "slidemill" type does not qualify.