I can't answer yet, because I have yet to get one, but my landlord requires that I have a tractor instead of a stationary coop so I'll be following this thread!
One thing that I'm not looking forward to is having to go out in the muddy back yard to move the thing around. (We have nice grass but it's so rainy that it doesn't stop the mud from squishing up between the blades!)
Good Question. The biggest problem I've had with mine is it's very heavy and cumbersome, not entirely easy to move without my husband. It has two wheels on the back of the tractor and a rope on the front to pull it with. I also wished it offered a little more protection from the elements. Living in Oregon we get a lot of rain and I noticed when the tractor is in use it doesn't offer my girls any protection unless they climb up above and go into the roosting area. Last but not least I wish it had a window in the roosting area. Luckily my tractor is not my main coop, its just a secondary area used for housing chickens that need to be separated etc...