A friend recently asked me for a car seat recommendation and I was surprised at how much I had to say on the subject. We have 2 Britax Boulevard seats that are two model years apart (2006, right and 2008, right). Fortunately, we haven't been in any serious collisions, so I can't really speak to how they perform their intended purpose. A car seat is like insurance, you don't know how good it is until you need it...and then its too late.
Along this thinking, we immediately were drawn to the most expensive models (those ones at the front of the aisle). While the majority of baby products all play on some level of peace-of-mind and guilt ("you can't afford not to have your baby in this seat"), Margret and I both felt that a car seat was one of the few things where you didn't want to cheap-out.
Once at the store, it was pretty obvious (by both price and quality) which were the premium seats. We spent over a half hour fiddling with all the seats and eventually decided on the Britax Boulevard. What the deciding factor? The color. I know that's a horrible reason to buy the most important protective device for your children, but I guess I'm just a little superficial that way. It was the most expensive, so that kind of offset the vanity (expensive=good, good looking=great).
The Boulevard is the biggest and heaviest of all the seats out there, but it also has the most padding and safety features. Since I shuttle the kids back and forth with me to work with me everyday, I wanted to make sure they were comfortable. After 2 years of daily use and 4 airplane flights, they have held us extremely well. The seat covers can be removed and washed, something important when you feed you kids donuts on the road. They straps are easy to adjust and the buckles are just tight enough that they girls can't press them.
With all that comfort comes a lot of weight. These are not the kind of seats that you want if you constantly switch seats between cars. Another thing to consider is that the seats are very wide. You can only get 2 of them across in a bench style seat. We did used everything short of a sledgehammer trying to get 2 Boulevards and a infant seat across a full-size SUV. If you plan on having 3 or more in car seats at the same time and don't have third row, you might want to consider something else.
All in all, our Britax Boulevards have held up to serious use and abuse and neither Ava or Mae have been able to escape from it clutches. Let's hope we never learn how well they perform in a fender bender.