[FLYIN']

I found US car seats to be far inferior to the European equivalents. For some reason US seats can't use mechanical connections to the Isofix brackets and they have to are belt tensioner that connect to them.
We ended up getting a Cybex seat from Germany. It's awesome as it swivels 360 degrees so you can buckle your child in the swivel to be rear seating so no wrestling with a belt and it's rock solid. I really don't know why US seats suck so much.
It's a 30 second swap from the X5 (where it is most of the time) to the M2.
When rear facing you do lose some legroom in the passenger seat but forward facing you can push the seat so the front passenger is as comfy as needed.