I only stay off-property and never will go back on property again. The Super 8 right by Old Town/Fun Spot (IT'S HUGE) was clean and nice for $32 after tax in August. We loved it more than All Star Sports and was 60% cheaper.
That said, only do it if you A) have a car B) only want a place to sleep, C) and most important READ REVIEWS!!! The resorts themselves do nothing as the parks are the draw to me.
Good point on "B". When my wife and I stayed at the Super 8, that was before we had kids and when my wife was still physically able/willing to do the parks with me from open till close. Although we had a total blast on those trips, I can't imagine trying to do any kind of midday break, or making a practice of only being in the parks until 4 or 5, then spending the rest of the evening at the hotel. Because for one thing, it is a 15 or 20 minute drive from that Kissimmee Super 8 to the gates of WDW, so it would be very inconvenient to try to drive back to the motel, then back to the park later in the afternoon. Once we would leave the park and go back to the motel, it would be with the intention of spending the rest of the evening in Kissimmee, either in our room, or out mini-golfing, going to Walmart, etc.
The other problem with staying off property, or at least at that particular off property location, is that there is no ambiance or ammeneties to make the lodging an attraction in its own right. At the Disney resorts, you can spend the rest of the day at the hotel, just enjoying the pool, surrey bikes, arcade, or just lounging around enjoying the ambiance. At the Super 8 we stayed at, it's either lay around in your room watching TV, swimming in the generic hole in the ground pool, or watching the traffic go by on the highway...not really anything to do at the motel in other words.
So again...for the OP, if you want to stay off property, either make sure that you plan to only use the lodging for sleep and shower, or make sure that it is close enough to Disney property that you can conveniently go back to the park later that evening if you want. And make sure it has enough ammeneties to keep you entertained at the hotel/motel. But, of course, that's gonna hike the price up, too.
And, as someone else said, if you don't have a car and you're relying on the hotel shuttles, just keep in mind that there are only a few times that the shuttle comes. I'm sure each hotel/motel is different, but with the Super 8 that we stayed at, if I remember correctly, there were two departures in the morning TO the parks, and two pickups in the evening FROM the parks. So you either go in the morning at one of their departure times, or you don't go. And you have yourself at the parking lot at the designated place when the bus comes, or you walk back to your motel. It's not like the Disney bus service where the busses are constantly running. So if you want to leave at 3 PM for a nap or swim at your motel, you're out of luck and are stuck there until the bus comes. And if you want to stay and watch Wishes at 10, too bad...your bus will be there at 7 PM and you'd better be there.