ive had no problems from a dirty back wheel, but often there will be some oil spray off the chain onto the floor, not to mention a big puddle of sweat so be careful where you set up your turbo.
I've been doing all my turboing in the kitchen rather than the garage, I can be semi socialble with the rest of family there.
I recently got a sufferfest download and I'm loving that as a way to make the turbo sessions much more enjoyable even if they make me work harder than i should for base training.