We have the Graco Quattro Tour Duo Stroller and I love it. It holds up to 50 lbs on each seat which is great and all Graco carseats fit. It has good storage space, each child gets 2 cupholders and a sunshade. The parents also get 2 cupholders. Its very easy to steer with just one or both kids in it.I can actually steer it one handed and fold with just one hand. Also it folds 20 percent smaller than a regular double stroller. that's a plus because I have a smaller car. Its pricier, about 240.00 at Babies R Us.
I originally got the Joovy Stand On Tandem and it broke! Not something small either, the leg broke above the wheel while my son was in it! I had taken the baby out and we were just on a sidewalk at it just snapped. I only had it a month and luckily still had the receipt and returned it. Another thing I didn't like about that one is that it was a pain to fold and get into my car and the carseat didn't lock in, there was a little seat belt that held the carseat. If the carseat wasn't placed just right, the clip wouldn't latch and there was no way to make it tighter or looser it was just one length.
P.S. My son is 4, but still loves the stroller, and I like him in there also!