
Nope.  I keep my Mac running all the time since it also acts as a
usenet node and exchanges mail and news every half hour (I run uAccess)
and receives all my faxes.

I do turn off the monitors hooked up to it.  They produce more heat
than I want - it can be warm in my garage office in the summer.  I've
got one of those handy power control centers ($25 at Fry's) to I just
flip the switch in front when I start or stop working.

By the way, this strategy seems to be somewhat endorsed by Apple since
their new Color Classic will turn off its own monitor after a certain
length of idle time.