I have to disagree with those that are proposing lower temp thermostats as
a cheaper alternative to either water or oil recirc systems.  

Engines are designed for optimum operation within a certain temperature
range.  Going much outside this range, either high or low, will reduce the
engine's efficiency, i.e. lower gas mileage and power, greater emissions,
significantly.  This applies to lower temps as well as higher temps.  For
those that want to go with a lower thermostat, try removing it altogether
sometime and see what effects that has on the above mentioned criteria. 
You'll see reduced efficiencies across the board. 

In addition, there's no guarantees that such action will have the desired
effect, that being to lower "engine off" head temps.  If the outside temps
are 110F in the shade and the engine's set a tad lean, I doubt it.  If
you've just pulled Monarch Pass in 90F heat and 20% humidity, I doubt it.
Thermostat's are designed so that engines reach operating temperature in
the shortest amount of time, but not necessarily to limit their upper
range.

The trick here is to get lower head temperatures in the cheapest, most
efficient manner possible, not just the cheapest.  Someone with a head
temp sensor and dash mounted readout should try the lower thermo fix first
under a variety of conditions and report their findings to the list before
people start swapping their's out willy-nilly. 

Just my $00.02, but I've seen the effects first hand on an engine that had
no thermostat, just what can happen.  These are intricate little beasties,
these infernal combustion engines, and when you start fixing things that
aren't broke, they will.

Jack