I've looked at two, the baby trend and one by century. The century one seems nicer to me; it looks just like a 'regular' stroller, reclines, canopy, basket, snack tray for baby, and one for parents on handlbar that's removable. It has a seat/footrest at the back of the basket for the older child, you just remove the snack tray so they can stand ( it also has seatbelt for older child).
The one I saw by baby trend looked like a giant frame to me. It had a baby seat up front, and a seat/footrest for sitting/standing in back. It did have a basket, but no snack trays, and I don't think there were canopys.
A friend and I are both expecting our second babies, and went looking at these. She had the people at BabiesRUs test both to see if they fit in her trunk, and they did (she has a Cavalier, so you have an idea of trunk space). She also checked and the baby trend model will accept the carseat carries from any brand if you want to snap that on to the stroller in the seat area.
Both were about $150, and were both at BRU. The biggest drawback I saw (on both) was that if you had the younger childs seat reclined, then the older child couldn't ride or stand - it blocks that area.
The main reason I preferred the century model was that the main seat seemed more comfortable, more the single stroller I have. The one on the baby trend seemed more chair like and less padded. Of course, my friend thought the baby trend was much nicer, so she got that one, so I guess you just have to look and compare.
I haven't purchased one yet, I want to still look some more, so I haven't really "test driven" them outside of the store. If you check, I think Consumer Reports did an article on double strollers a few months back that did include some sit and stand models.
HTH!