I have one also and just used it this morning. It works great for me although I did have to take the first one back because it did not work. Anyway, I like being able to wind bobbins off the machine when needed.
PS: If I remember right, you have to make sure it will accommodate your particular make machine bobbins. I think it tells you on the box what won't work but it's been a couple of years since I bought mine so I am not sure that is still true or not.