I'm actually pretty surprised how cool (temp wise) my Shuttle is. With a 2.4GHz CPU (non-overclocked), TI4400 video card, 7200 RPM hard drive, and a cdrw:
load
system temp 45C
CPU temp 50C
idle
system temp 43C
CPU temp 33C
I'm pretty sure my old computer was a lot louder and hotter. Go figure.