Great option for preschooler and infant
I researched double strollers for a long time, going back and forth between getting the Joovy Ultralight or a side-by-side (Maclaren/other umbrella or City Mini double). We live in NYC, so we use the stroller every day, and walk pretty long distances (up to 6-7 miles in a day). I am so glad I got the Joovy and not a side by side. In the couple of weeks that I've been using the Joovy, there have been multiple times when a side by side would have been very difficult to negotiate. My older daughter (3 yo) loves the option of standing or sitting, and really likes being able to see her baby sister (6 months) or hand her a toy. We have the baby in the car seat, which does make it a little harder to push and steer, but it isn't terrible. We also have a single City Mini and single Maclaren volo, so that's what I'm comparing it to. The other reason why I'm glad we got this and not a side-by-side is that the 3 yo often wants to walk. Holding her hand and pushing this with one hand is easy. Pushing a half-empty side-by-side and holding her hand seems like it would be a pain.
We initially tried putting the baby in the regular seat, but she didn't seem very comfortable in it (she can sit up on her own but still seemed slouched over it in), and definitely didn't like not being able to see us. For the most part I keep the second seat in the bottom basket (it just fits, and is difficult to get in and out-- I slide it in under the bench seat), and install it when we're going to walk for a long time or at the end of the day when my older daughter might want to nap or just chill out. It is very easy to install (less than 5 minutes). I will say that if you have bigger kids it might be a bit small. My daughter is 34" tall and seems comfortable enough in the rear seat (though not as comfortable as in the city mini). Her legs seemed a little long for the footrest when she tried out the front seat.
There is very little storage (especially when we have the second seat with us), but I got some stroller hooks and that has worked fine. Also, with the infant car seat in place you can put items like blankets or a small bag on the front seat under the car seat (just make sure to strap in place).
I think this is the smallest option for double strollers. It definitely feels heavier than ~20 lbs, and is a little awkward to carry around, but we got it on a bus (folded) without any problems. Can't attest to durability but so far it seems well made.