The Flipstix are 6-inch double-pointed needles. What makes them different is one side is more pointy than the other. One side is the "Turbo" tip and the other is the "Lace" tip.
Above - the "Turbo" side
Above - the "Lace" side
They're made of aluminum - I found them comparable to most of the other metal needles in my stash. I wasn't super wowed by them. That's not to say I didn't like them, because I did. It's just I wasn't knitting with them thinking to myself "these are the greatest needles of all time!!! Ahhhh!!!" You know what I mean. :)
After I trained myself to make sure I was using the lace side of the needle, things went quickly. I finished that hat in just a couple hours.
While I did like them, and they were definitely fun to try, I'm not so sure I'd buy more of them. It's nice being able to have one set of needles that can be used in two ways. If you're on a budget and want addi double-pointed needles, this is a great option for you. Honestly, I'd probably just buy two different sets of addi dpns so I wouldn't have to worry about making sure I had the needle flipped the "right" way.
And, as a knitter who tends to keep her double-pointed needles extremely unorganized, the fact that they are all different colors is going to make it difficult to find the entire set when I go to use them again. Perhaps you're more organized with your needles, and that won't be an issue for you though.
So, basically, I liked them. I didn't looovvve them like my addis lace circulars. :)
Have you tried the Flipstix? If you have, I'd love to know what you think!