The plastic macbooks do not disperse heat through the case the same way the aluminum MBPs do. As such, the bottom of the Macbook has more concentrated heat, whereas heat is distributed across the bottom of the MBP.
Nothing to be too concerned about. the hardware integrity is not compromised.
I was reading reviews of the MacBook Pro 13" less-expensive version, and several of the people who owned it said that it gets extremely hot on the bottom. No similar complaints for the higher-priced one. Does anyone here know about that? It was not just a couple of people, but quite a few.
I'd really like to know whether this is a widespread problem or just the bad luck of some MacBook Pro 13" owners. If it's very common, I think I'll just go with the pricier one, but I haven't decided yet.