The MR65 is a GREAT seat! I don't have one and have never used one but car seat tech's all over the place are LOVING it! And kids love the 2 built in cup holders!
Other car seats that I've heard great things about that are not Britax are:
First Years
True Fit and
True Fit Premier - both very tall and should get MOST kids to booster seat age. The Premier has an anti-rebound bar that takes the place of rear-facing tethering that Britax does. This is on my list of car seats to own someday! lol!
Sunshine Kids
Radian 65,
Radian 80 and
Radian XT
I have Radian 65's for both of the kids, use one rear facing and one forward facing, and LOVE them. They get exceptional head excursion numbers, even without a top tether so I feel better about using them in the vehicles that I don't have top tether anchors in. The newest (Sept. '09) Radian XT's have just been certified Rear Facing to 45 lbs!
The cosco scenera is a fabulous seat in it's class - I bought one a few years ago when we accidentally left Kyrie's car seat in G'ma's vehicle and then she drove home (80 miles), and we use it for a backup / daycare seat now. Since it doesn't have any extra side impact protection or energy absorbing foam, I don't like using it for a main seat because of all the highway traveling we do, but it's not by any means a bad seat!