You can read the product details on Sephora.com and watch a video demonstration:
http://www.sephora.com/browse/product.jhtml?id=P296010
While in the store, I bought only one color, House of Parliament, for $16. Very pretty metallic purple. I pretty much did exactly what the sales lady did in the store: apply one coat, then hover the magnetic cap over it while still wet to attract the magnetic particles to create the design. Some nails were more successful than others. Then, I read the instructions, which say to lay down one layer to let dry, then apply a thick second layer for the magnet effect. Again, some success and some less successful. A thick layer does help make a difference, while I think one thick coat is sufficient rather than two. Be careful not to touch the wet polish! I also watched the 15 second action between the nail polish and the magnet, and I actually saw the nail polish gravitate a little mountain toward the magnet. Kinda cool, but you also gotta watch out for that because sometimes the polish rises so high that it touches the magnet, and then smudges!
quick iphone pic:
So, I think it's pretty cool. But $16 a bottle is a bit much for my nail polish budget. I probably won't purchase another bottle at that price. Hopefully there will be a sale, coupon, or a cheaper competitor sometime soon.
Products mentioned were purchased by me, and opinions formed are my own.