The Phil and Ted's E3 is a single jogging-type stroller, but you can hook a second seat on. The maneuverability is unbelievable; there's never a worry about whether you'll fit through the door. The combined weight limit for the two seats is 88 lbs., but luckily the air-filled rubber tires make pushing fairly effortless.
The downsides: price (although I imagine the resale value is pretty good), lack of storage space (we sprung for the panniers, which you can see in the photo), and the possibility that the kid in the back will want to touch the spinning tires of death. People often comment that Beatrix, seated in the back, can't see anything, but she has plenty to see out the sides. At any rate, she's never complained!
In addition, if your kids are really close in age, I probably wouldn't recommend the E3. I'd check out the Mountain Buggy Urban Double, or something similar. The beauty of the E3 for us is that it's a great single, with the capacity to be a pretty amazing double.