I have an Intel Core Duo 2 Macbook Pro and I must say it is not nearly as hot as my brother's late model Powerbook G4.
My MBP is actually not so bad, it keeps my legs warm. I have not yet felt like it is going to burn me, whereas the PB felt like it would burn you.
That's why Apple turned to Intel, Motorola (or whoever was making the PowerPC's) could not deliver a G5 chip for a laptop that would not run unsafely hot.