J.C.
I recently saw this amazingly sad video all about this Britax Regent and the importance of ahving kids in boosters as long as possible. (I am sure you've all seen it but in case not here's the link http://www.youtube.com/watch?v=azgBhZfcqaQ )
It is definitely by far the safest to keep your child into a five point harness for as long as you can and I am unaware of any seat other than the Britax Regent that does so up to 80 pounds, although I am sure there are more, but I am a huge Britax fan. I actually put my 6 year old BACK into a 5 point harness after taking her out and putting her into a booster after I found the Regent.
Now's a good time to scour online for deals on Britax too since the 2007 models are just coming out and the 2006 models.colors are being discontinued. I just bought a roundabout for my 11 month old online and think I got a great deal. Good Luck!!