First off, I misread the title and read it as "Mattress Races" instead. I was disappointed when I saw my mistake.
Secondly, I have slept on just about everything besides a sleep number bed. Standard, Memory Foam, Waterbed, Watertube Bed, Hybrid Water and foam/memory foam mattress, etc.
I currently am sleeping on a 7" cheapo memory foam bed and it is some of the best sleep I have ever had aside from a ridiculously plush bed I slept on while on vacation in Hawaii once.
I would say, that if you do go for another memory foam mattress, make sure you get one that is plenty thick as my knees do tend to sink down to the frame when I'm, ummm not sleeping.