We rented them last year for my 2 1/2 and 3 1/2 year old.
Pros:
They are huge. The two kids fit easily (everywhere but MGM where they are umbrella stroller things). We saw plenty of five and six year olds in strollers.
The were really easy to push - lots of double strollers aren't.
We didn't worry about folding a stroller to get it on the buses or stollers at the airport.
They are really easy for kids to get themselves in and out of. Both my kids could do the straps and get in and out by themselves. (This could be a con I suppose, but for us, it was a pro, since we didn't spend ANY time lifting kids in and out of the stroller, and they got in and out of the stroller ALOT)
No worries about the stroller getting stolen. If we couldn't find it (and we always could), the receipt would get us a new stroller - as well as a stroller in any other park we visited on the same day.
Cons:
They aren't cheap. About $15 a day. In the scheme of what we were spending at Disney, it wasn't much, but I know that for a lot of people $15 a day in stroller rental is significant.
You only have it in the parks. That can make the walk back to your room at the resort with tired kids a long, heavy one. (I'm not sure how much easier it would have been with our own stroller and bus transportation where we'd have needed to get tired kids in and out of the stroller, however).
You do have to rent it every day. We discovered at the stroller parks (particularly MK, where we started most mornings), before opening there were people dealing with "stoller express." My husband would give me his bag to have checked. The kids and I would do the security line, he'd give cash to the stroller express person and get the placard that goes in the back of the stroller. Once the gates opened, we showed the placcard at the rental station, and they gave us the stroller. Whole process never took much time (maybe an extra two minutes), but some people don't like the inconvience of renting (or don't find the stroller rental express and need to stand in the long line to rent).
They don't recline. They really aren't built for napping. They are also molded plastic and don't look very comfy (we had jackets and such and the kids didn't complain).