LOVE this thing!
I have the Emjoi Nano (plug in version) and I really like it.  But, I thought this one looked a little easier to handle, so I got it.  I honestly think it has more power than the smaller one, and it is easier to handle.  During the winter, the tips of my thumbs and index fingers tend to split (very painful!).  I use the callus remover to keep the dry skin on my finger tips filed down.  I find that if I do that it greatly reduces the number (most of the time I get none) of splits I get during the winter!  I even use it on the back of my hands because my knuckles will split, too.  I love both of my Emjoi callus removers and use them a lot.  I personally prefer the corded models because I get tired of buying batteries.  The cord is fairly long.  I'm not sure I can speak to the 3D power, but I just used it and it works great!
Rating: 5 stars