I'm not normally on the side of the Disney apologists, but I have to agree here. They key is this: would you expect the same of any other company you deal with?
If you checked into a Sheraton hotel and their pool was closed, or a Hilton and the free breakfast didn't have the items you wanted, would you expect "compensation"?
If I paid for a first class seat on an airplane, I would expect to get a first class seat. First class seats usually come with better food, better entertainment, etc. than in coach. But if my in-seat entertainment system wasn't working properly, or if they ran out of the steak before I got any, I wouldn't expect "compensation". However, if they stuck me back in coach, I would expect "compensation" - the cost difference between a coach seat and what I actually paid.
Similarly, if I paid for a room at the Poly but they put me in a room at All-Star movies, I would expect compensation. If I paid more for a "Theme Park View" and got a dumpster view, I would expect compensation for the premium I actually paid.
Here's another way of looking at it. Presumably, Disney is still taking reservations for the Poly, even during construction. Do you think they're charging super-low rates because of the construction?
If they are charging lower rates now, you might want to cancel your reservations and re-book.
If they are not charging lower rates now, then clearly the part-time loss of the monorail isn't worth anything.