I must point out here the electrical cost of such a device. The power you use to run this thing would pay for a commercial chest freezer every year if you leave it on to cool drinks or film or something.
However, they do make an awesome science/technology demonstrator and are good for getting *huge* temperature differentials, which means you can do stuff like get semiconductors down near the point of liquid nitrogen and therefore build stuff like far-IR (longwave) infrared cameras that can see body heat, etc.
I actually had one of these in my PC for about a year for overclocking purposes; of course waiting a year for the next model gives a performance boost just as good as all the refrigeration and plumbing that I built, but you learn a lot about thermodynamics and how control-systems can interact badly with physical systems - a traditional bang-bang thermostat will destroy a Peltier by thermal cycling shocks so you need to build a PID controller with PWM output if you want to have a controlled temperature. You don't want to discover that failure by smell on your PC...
If you like a challenge, try building a multi-stage cooler and keep both stages running in their efficient zone.