We've had our Mountain Buggy Duo for three years. Aside from fading because we leave it out sometimes, it has held up very well, and performs like new. Here are some of the things my wife and I love about it:
1. I LOVE it because the handlebar can go super-tall. I'm 6'2" with long torso and short arms (a comic image, I know), and I can raise the handle high enough such that I can keep a very good posture. My neighbor who's three inches taller borrows it when he's sitting his granddaughter for this exact reason.
2. Stability & Width- I'm sure there are more stable options out there, but a double that fits through every door we've ever met? It's amazing, a three-year-old, and a newborn, through the doors, over curbs, in between clothes racks in the Macy's, at the rodeo fairgrounds, the park, the street, we have yet to upend it, even with older siblings driving.
3. Built in pump- I threw in a $2 patch kit, and the pump that fits inside the cargo holder makes it a complete kit. Saved our day at the amusement park last year.
4. Stroller & Jogger- Lock the front wheels straight and run as fast as you can. Did I mention it's stable?
5. Indestructible- I know I mentioned that it has held up well, but now that I think about it, our kids are really "active". And as parents, we tend to neglect protecting our stuff against them (except for my surfboard). The Mountain Buggy has been used to haul pets, rocks, potted plants, and probably a million other things I don't want to think about. As I said, aside from the fading, it's as new.
6. It looks cool. We're kinda vain, and like to be perceived as hip and stylish with a splash of functional. Done.
7. It folds up super tight. You don't have to take anything off or apart. Although, if you're super-short on space, you can remove the wheels without tools.
8. Great accessories- Storm covers, carry cots, shade covers, drink holders, cozy little sleeper bags, etc. There is no shortage of cool things to buy for it. We've only added the storm cover, but we flirted shamelessly with the idea of buying a carry cot.
What's not so great:
-The release latch to fold up the stroller wasn't quite right. At first you had to get a large flat-blade screwdriver to get the tab to clear the foot dasher board. I'm sure it was an assembly defect. I fixed it myself, but I was bugged about it.
-I mentioned that the fabric faded. Of course that's because we left it out a lot, but we leave out a lot of stuff, and this seemed to fade faster and harder. I'm guessing the fabric is not UV resistant. Maybe they've changed that in the last three years.
-Tires, we put a lot miles on the tires. I didn't think they were super high quality anyway. I had to put new tires on after two years.
-Parking brake- It works very well, but it's painful to my toes to take the parking brake off when I'm barefooted (you're probably wondering why we're parents by now ;) ).