I have a B Agile, and it has gotten very minimal use in the 6 months that I have had it. It now squeaks and does not steer very well. I'm very disappointed as it isn't a super cheap stroller. I love Britax car seats, but I'm not impressed with their strollers.
I do have a BJCS and love it! It is perfect for my two boys. I really like all the different configurations, and my baby doesn't have to be so low to the ground like the B Ready. Also on the Select each seat can go to 45 pounds, whereas on the B Ready, the bottom only goes to 35 pounds.