DH and I bought the Uppababy vista when we had LO. It is an awesome stroller. We bought the Peg Perego car seat to go with it and had no complaints of that either. However, now we're expecting again and LO is only 11 months tomorrow. So we had to get yet another stroller but this time a double. We picked out a Britax and with it you can only use a britax car seat. So we are selling our peg perego car seat and we found a fairly new britax car seat in excellent condition on craigslist and bought it for $100 off.
That's what we're doing but my advice to you would be. If you're planning on having this baby and not another one for a long time, go for the city mini. But if you're planning on having more kids fairly soon, I would do more research on while car seat/stroller to buy and then what double stroller would you get later on.
The Uppababy vista has the option to have 2 kids in at once but we didn't think about how the older one would feel in the stroller when we put the infant in it. DD1 would be facing the back of the 2nd baby's car seat and not have a view of anything. So really just do a lot of research. Especially when you're investing a lot of money into this. We did a lot of research but are now stuck with an expensive stroller that we don't need and had to get something else.
Hope that helps...at least a little. :)