I'm also having heat issues with my Macbook Pro ( spec in signature )
It's running at 70 degrees celcius with Safari, Mail and iTunes.
When I have ArchiCAD opened it runs at 90 degrees C and when it's starting to render, or using photoshop it runs upto 105 degrees C and have on a few occasions reached 106 degrees C !
I'm also having constant crashes, the whole enclouse is extremley hot and overall the computer is slow... I've now sent it to a Apple Authorised service provided ( through applecare, group 8 UK ) for inspection... If it comes back with any of the above issues, I will be asking for a replacement ( they put me straight onto level 2 support when I told them what temps I have and said that an inspection is needed before they can offer a replacement ) I also spent 2 hours on hold with them whilst they transferred my HE Applecare to this machine although I was told it was transferred before Christmas 2009 !
But hey, I know Apple will take care of me 🙂
EDIT: I'm using iStatPro