DD1 has a Britax Boulevard. I've mentioned in the convertible carseat threads that I didn't recommend it.
First off, she outgrew rear facing around 29 months old. She wasn't near the height and weight limits advertised by the seat, but her head was within an inch from the top of the shell. I was disappointed to have to switch her so young.
Today I just realized that harness is at shoulder level (it should be at or above) and that the harness is already in the highest position. So at 3 years and 9 months old she's outgrown the seat entirely. She's 32 pounds and 35 inches tall. The advertised weight and height limits are 70 pounds and 40 inches.
She's too young, too little and too immature for a booster so now I'm in the market for a "combination" seat, which will run me another couple of hundred dollars.
I went with a Britax because that was what was recommended to me. I admittedly didn't do a ton of research. In hindsight I wish I had researched more myself and gone with something with higher limits, allowing for longer rear facing and hopefully, longer forward facing. Three carseats in under 4 years just seems wasteful to me.
DD1 4.14.10
DD2 8.22.13
MMC 1.4.17 at 16w
Expecting #3, EDD 1.29.18

Re: Convertible car seat- another Britax comment
DD2 8.22.13
MMC 1.4.17 at 16w
Expecting #3, EDD 1.29.18
If you want to RF her again the mysize70 is a great seat (about 150 if you get it on sale) and will probably FF her until booster age with 17.5 inch tops slots (and boosters are cheap)- you could also use this to just FF, but a convertible is silly to buy if you aren't going to RF.
Nautilus will give an extra 1/2 inch more than the mysize with 18 inch top slots.
Anything longer lasting will be the Britax combination seats.
I fell for the "britax bubble" for my first kids, it was a very expensive lesson to learn!
DD2 8.22.13
MMC 1.4.17 at 16w
Expecting #3, EDD 1.29.18
We went with a Brotax Frontier as a combo seat bc I'm not ready (notwithstanding the fact he's not 4 yet) to put him in just a belt positioning booster.
Our other seat is a Diono radian and while the manufacturer says their shoulders can be above the straps FF, I'm not comfortable doing it. We'll prob switch him to a HBB w a 5pt harness like the Frontier when the babies make the move to convertibles regardless, though.
Granted, he's a big kid with a long torso. But I would like to keep him harnessed as long as possible and a Frontier does let you do that.
Unfortunately the short shells of the britax are outgrown long before the height and weight limits. I know lots of people that have had to go buy another seat for that very reason.