I've stated at the Holiday Inn that's further away from DLR...not sure what street its on. But we used the ART shuttles, and that worked out fine. Just have to ask the front desk which route your hotel is on. I think a new shuttle comes every 20 mins starting from 7:30a-12:30a. It was $4 a day to use the ART as much as you needed.
Our shuttle was always on time.
BUT a few months later we stayed at this place on Katella, which was walkable but my mom has a bad knee and we had breakfast reservations so we took it one day. It was FULL but we squeezed in. Later on, my sister went back for a nap and said the shuttle never came so she ended up walking. Then that night we were at DLR waiting for our ART bus, which was route 12, and we saw it pull up to the route 1 stop, pick up those people and never got us!! We walked again. Thankfully we were staying within a reasonable walking distance!!
I don't know of any other shuttles besides the ART but I guess it's a hit or miss with them.
I would personally stay at a cheaper place closer to the parks. It's just easier to walk. I know lots of people here talk highly of the Candy Cane Inn, Best Western Park Place and the HoJo.