Just thought I would chime in briefly as a B-ready owner, for anyone who finds this thread useful. We have only used it as a single stroller so far, but here was our experience:
Overall we were very happy with it - it was easy to push and turn, and we loved to be able to have our daughter up high and facing us. As she got older, she was able to climb in and out herself, which I thought was unexpected. The storage underneath is awesome (we have used the carriage more for hauling kiddie stuff around than for the kiddo :)). We have the chaperone car seat and have loved that - found it really easy to use in a number of different taxis and rental cars internationally (just be sure to call Britax as soon as you get it to ask them to send you the locking clip - it doesn't come with it automatically, although they will send it to you for free, and you may very well need it, especially with international travel), and super easy to install correctly, and to take in and out of the car and or the stoller while a baby is sleeping in it. Our daughter actually napped exclusively in it for a while, because there was a whole stage when she would only go to sleep if we rocked her in the carseat (the way it is constructed, it is really easy to put it on the floor and rock it back and forth with the baby in it.) It has been wonderfully durable - we have literally had it halfway up a mountain, on long treks on gravel, on cobblestones, on city streets, through sand, etc, and it has held up well. The main seat has also been a great place to put other carseats once she outgrew the Chaperone - during travel abroad, we were able to put a regular carseat in the Britax seat, hang a large backpack off the handle, put the dog carrier into the carseat, and stuff another carryon under the stroller - so that all we had to do was to push that through security (although this was only helpful if you could gatecheck the stroller, which often wasn't possible in smaller airports or in Europe). Even though it is somewhat big when folded up, we were able to fit it into a number of taxis and European (read small) rental cars along with a ton of other luggage, mainly because breaking it down into two pieces instead of one gives you better flexibility in putting it where you want to. This stroller was also awesome for us because we are both tall - 6'2" - it was one of the few that we could use without kicking the back (although I don't know if that will still be true with the second seat?).
My main complaints: the back wheels are wide for stability, which is good, but they are so wide that sometimes this is a pain - I think it is because the wheels are wider than the handle, and so I sometimes trip over them because my eyes are tricked into thinking that they are not as far out as that (it still fits fine through doorways, etc, though). The five point harness is a pain because the top and bottom parts don't click together - you have to hold them together while you try to click them in, and if you don't put pressure in exactly the right direction, they can slip apart as you try to click them in - with practice you get used to it, but I still wish they would find a way to have the top and bottom strap click together first! There is no handle on the side or any way to carry the stroller when it is folded up and you have a kid in the other hand/arm - while it folds up well, it is awkward to carry once folded (and heavy!). We have also had trouble gate checking this stroller at airports about 20-50% of the time - I don't know that this is really a downside per se, as anyone who always wants to guarantee gate checking a stroller would need to buy an umbrella stroller anyway. I would also note that with the seat installed so that the baby is facing you (which is the way we always had it) it doesn't really fold well - you are actually better off reversing the seat, and then folding it.
We just recently bought a Maclaren XLT for my now almost 2.5 year old, because we are abroad for several months and the airline wouldn't let us bring the Britax without paying something like an extra $500 to check it (because our daughter is over 2 years old). In comparison to the Britax, the Maclaren is very nice, in that it is smaller and has a much smaller turning radius, and is much lighter, so it is much easier to haul onto the subway, etc (we live in the city). But I never would have bought the Maclaren for a newborn, because I really wanted to be able to see my newborn, and to have her up high and facing us, and I also really appreciated being able to use the carseat as the seat early on with the built-in easy method for just clicking it in and out, and to be able to easily take it in and out of taxis and cars. We weren't big stroller people anyway - I mostly (even now) always carry my daughter (or she walks) and we mostly used the stroller for longer day trips or for travel, mostly so that DD had somewhere to nap on the go and/or so that we had somewhere to store the diaper bag and food and toys, etc. My MIL is in her 70s and watches DD a lot, and since she can't really carry DD, she used the stroller a lot. I have no regrets about having the Britax, even though I'd love to see a few improvements and even though we don't use strollers a lot, and we plan to get the second seat for our upcoming second child.