We've got a moderate heat problem in the office. It's been noted that it's not as bad when my systems have been shut down, which leads me to believe the SGI is the main culprit. To that end, I'm trying to use just the iMac today. The SGI, these days, has three purposes in life: 1) telnet client; 2) X server; and 3) MP3 player. The iMac can do all of those.
The biggest loss would be in giving up the screen real estate (1024x768 on the iMac, instead of 1280x1024) and the nice 19-inch Trinitron monitor. OTOH, I would be able to move the TV and VCR to where the monitor sits now, next to the iMac, and both reduce some cabling clutter and make room for the ham station.
It does feel strange to be thinking about moving out a Unix box in favor of a Mac. Just goes to show how right Apple has gotten OS X.