This is the frequent configuration of my desk in my home office lately. That's a MacBook Pro sitting on top of a PowerBook. I've been doing some things lately where the MBP is a big advantage, so have been bringing it home, even though I have the PowerBook to use at home. The PB's days may be numbered.
Note, I don't have them both on (i.e. fully awake) at the same time. The MBP is currently on and in use, but the PB is sleeping. I also use the handy smcFanControl to ensure the MPB's fans are cranked up and keeping it nice and cool.
I am the VP of Engineering at DealBase.com (the largest hotel deals web site), an independent software developer, as well as VP of Engineering at Bring Light. And for the non-professional side of life, I have a great family with two small kids, love to ride bicycles, and enjoy living in Eugene, OR.