I've stayed at the Downtown Disney Doubletree. The rooms are all 'suites' - it's nice to have the extra space. It's a clean hotel, but the rooms aren't really nice or swanky. They rate it a 4-star on the Hilton website, but it's really more of a 3-star. The lobby is nicely renovated, though.
We did use the bus system and it was horrible.
The first bus comes at 8:00 - try to make the 8:00 bus if you want to get to the park at opening time. The good thing about the Doubletree is that it's the last stop on the route, so you don't have to wait for guests at other hotels to board. However, later in the morning, the bus is often too full to be able to get on. Then you have to wait a half hour for the next bus to come.
The shuttle ride home was miserable. They filled the bus at Epcot, then went to Hollywood Studios and crammed more people on. We were packed on there like sardines, and it was hot. And unfortunately, we were the last stop on the way back.
Also, be careful about the names listed on the top of the bus. Our second day there, the first bus said "Magic Kingdom/Animal Kingdom" and the second said "Epcot/Animal Kingdom." We needed to go to Hollywood Studios, but didn't get on the bus because the driver had listed the wrong name. After taking our concerns to the manager, we were provided with a car service for the remainder of our stay, so we didn't have to deal with the horrible bus system anymore.
Here are some photos of the resort if you're interested:
http://www.flickr.com/photos/65057597@N07/sets/72157629734368868/
And if you want to read more about my annoyance with the DTD shuttle system:
http://www.disboards.com/showpost.php?p=44858512&postcount=48