Corby Kummer, author of The Joy of Coffee: The Essential Guide to Buying, Brewing, and Enjoying, says the stovetop moka brewer (like this one) is a low-tech, simple-to-operate, inexpensive (about $20) brewing system that produces a superb cup of coffee.
Kummer suggests purchasing a stainless steel brewer -- aluminum can produce off-flavors in the coffee. A good moka to try is the Carmen Chita Moka Club by Lavazza. If you are compelled to go all out, Kummer recommends a pump machine with an adjustable filter holder. A good choice is the Saeco-Rio Vapore sold by Starbucks as "Proteo." Be prepared to spend around $350.
Using a moka
To make coffee in a stovetop moka brewer, first unscrew the base, remove the metal coffee filter and fill the bottom with cold water to the level of the safety valve. Replace the filter and spoon in enough ground coffee to reach the top. The grind should be medium-fine, about the same as for a paper filter or a little finer. If the grind is too fine, the water won't get through it because the pressure isn't strong enough, or the water will overheat in the attempt and overextract, drawing out bitter substances. Sweep a knife edge or spatula over the top to level the coffee. You can compact the grounds slightly with the bottom of a glass that fits the diameter of the filter, but don't tamp the coffee hard or the water won't make it through.
Screw on the upper chamber and set the moka on a medium-low flame. After about 3 minutes, coffee will begin to hiss and dribble out two holes at the sides of the tube in the upper compartment. The tube in the upper compartment is by design partially closed, both to prevent coffee from spraying all over the stove if the lid is left open -- as it generally is, so you can tell when the coffee is ready -- and to add a bit more pressure to the coffee on its final journey. Some people even buy small metal caps that fit over the tube and further restrict the flow, supposedly to intensify the flavor. These don't do very much.
As soon as a dark pool collects in the bottom of the chamber and the flow of liquid changes from a slow and steady stream to a sputtering foam, turn off the heat. This will safeguard against burning the bottom of the pot. To get crema, advanced moka users fill the filter with coffee ground almost as fine as for a commercial espresso machine and tamp it before brewing. This might intensify the flavor, but I don't recommend it, because you run the risk of burning out the rubber gasket.
If you simply leave the top open and take the pot off the flame about midway through, you can obtain espresso better than many people ever get in their electric steam espresso or even their pump espresso machines. Don't get hung up on producing crema. If you do get any, think of it as some astral blessing.