Just in case anyone is wondering, our twins still ride rear facing in the car. I bought their Britax Marathon car seats for the specific reason of keeping them rear facing for as long as possible, which will be up to 35 lbs and 49 inches. When both Maija and Micah were little, I turned them forward facing as soon as they hit the one year mark. Obviously they both turned out just fine. Since then however, I have learned a lot more about the ways in which the impact of a crash will affect a child's body depending on which way they are facing when the accident occurs. There is plenty of information available online these days, and I have found the most compelling arguments for extended rear facing to be in the crash test footage.
If you are on the fence about this decision, take a few minutes to watch these videos, you will need to scroll down the page a bit, but I think you may find them to be quite helpful when making an educated decision for your family.
Otherwise, do a search of your own regarding "extended rear facing" you might just be surprised by what you find, I know that I certainly was.