I have three firepistons and like them very much. Vastly easier to use than bow or hand drills. Much like traditional flint and steel where a mild breeze is to your advantage.
They are a bit bulky and work best with tinder fungus so for me are just one more interesting way to make fire. I would not hesitate to use one over a hand drill any day.
Mine are made by Darrel Aune and Jeff Wagner. Top notch devices and from reading of many who have tried to make one....not too easy.
Darrel offers a DVD of his techniques and makes it looks pretty easy for a metal tube type device and if you are good with a lathe pretty easy then also.
Here are a couple of links to articles. The first by a friend of mine on the EBprimatives piston.
http://outdoors-magazine.com/s_article.php?id_article=284And the second by my friend and myself on the Aune pistons...among other things he offers.
http://outdoors-magazine.com/s_article.php?id_article=320