I have a CPR CS90 on mmy 55g tank.. It works great.... It was a pain and constantly wanted to overflow without using some sort of pump.. I ended up going wiht an Aqualifter pump and have never had an issue since... I am having a custom u-tube overflow that will handle atleast 1600gph made for me by a friend so hopefully i will have the same luck..
I really like the CPR style overflows though.. And thats a personal experience.. Just get the 12.00 aqualifterpump that goes with it.. check out www.amekaaquatics.com
and you can get factory seconds on the stuff for pretty cheap as well..