I have one and like it for the same reasons listed by others. It also winds bobbins tighter than the machine so there is more thread on the bobbin and it lasts longer. I also have a machine (with a separate bobbin motor) that gets really fussy about winding bobbins sometimes and this works when the machine is acting up.
I got mine on sale for about $15 when they first came out.
You can also occupy the kids by having them wind bobbins for you! lol