I have the oval Crock pot with removable liner. This is the second or third one I've had. It's still going strong after 10 years.
My daughter got one of the fancy ones that will take more than one size crock. It was not very satisfactory and I haven't seen them in the store lately so apparently she was not the only one that had problems with that style. It sounded like a great idea...Anyway she got one like mine to replace it.