OK girl ... per your request I tried it and I have to say that, while it turned out nice and neat it isn't something that I plan on doing again. I used a half jar sample of Ell-if-I-Know from the LOL3 collection to try it. Here are a few thoughts:
1) compared to pressing the MAC pigments the minerals took about four times as long to dry ... with the pigments I wait about half an hour ... this was still wet to the touch after an hour.
2) I used a half a jar of minerals to do this, and it just covered the bottom of the pan. Which means that if I were to use a whole jar the pan would still look half empty. With the piggies I was using about 3/4 teaspoon for the fullest pans.
3) They press really nicely because they are so finely milled. You can really see the pattern of the fabric!