How's the ride on the Mockingbird - is it good on most terrains? What are the wheels composed of? Suspension?
The Mockingbird stroller, even if quite similar to the Uppababy Vista, is a bit harder ride than the Uppababy. There's some shock absorption but you'll feel the bumps a bit - I would more suggest this being used as an urban pram. It's a much simpler, much cheaper stroller so you will feel the shortcomings more. This is only logical, I mean, the stroller price's always reflected in the stroller performance.
The Mockingbird wheels are made out of EVA foam with a bit of a rubberized surface. Take the stroller's wheels characteristics and performance as that of the usual EVA foam wheels - it's OK but there's going to be some wear over time. Not the most all-terrain wheels but you'll get over most normal "terrain" just fine.
Now, just a personal opinion - to me, this stroller feels a bit like a copy, which I am not so fond of. But for the price, it will serve you OK if not put too much strain of, and the steering will be good also thanks to the rotating handlebar adjustment, Don't expect too much and you'll be happy with it.