I LOVE the Double Elite Sit 'n Stand from One Step Ahead (onestepahead.com). I've bought many things from this company over the years and have yet to be disappointed. I bought this stroller more than 2 years ago when pregnant with my 3rd child. My older 2 used it as a Sit 'n Stand for a few months before the baby was born. When baby was born, the older kid got the boot, I put the backseat into the stroller for my then-2-year-old and put the baby's 'bucket' seat in the front. For the past 6-8 months it's been exclusively in the Sit 'n Stand configuration since my middle child is now 4.
This stroller is the only one I've seen like it. It takes less than a minute to convert it from a normal double stroller (backseat has 5-point-harness, footrest and sunshade) to a Sit 'n Stand model (bench to sit on facing backward, platform to stand on). The front seat has a tray with cupholder, the parent's have a tray with small storage compartment and 2 cupholders. The storage basket is large enough to hold several bottles of water, my diaper bag, a few towels and whatever else the kids need stashed during a long day at the zoo or state fair.
It folds easily, fits easily in my car (same size as my single Graco stroller when folded!) and is easy to manuvuer - even with 90 lbs of kid on board! I've used it at least 4-5 times a week for over 2 years and it's still in great condition so you don't have to worry about it being sturdy.