WE've flown with our Boulevard, but only with DS having a seat (we got it once he needed a seat, actually).
I asked a few months ago about checking the seat and many folks, as I had feared, warned against it. I've seen how car seats, even gate checked ones, are just tossed around, often just tossed to the ground. In my mind that could damage the seat as much as being in an accident. So I was very hesitant about checking it.
Is there any way you could get around this? You might consider some kind of box for it....(maybe get a Blvd box from babies r us, even?). Or, if you're visiting relatives, have them buy a seat to have on hand there for frequent visits, find a family to borrow a seat from, etc.
Given the expense of the Boulevard I'd definitely be careful in terms of checking it.
Mommy to an amazing 8 year old, wife to an inspiring principal, and welcoming Wylie Grace! Our July 4th babe!