If you are talking about the Sidewinder, I don't have an opinion. However, I would like to tell you about the bobbin winder I purchased several years ago from my dealer. I think it was intended for long arms, but it has a vertical feed rather than horizontal like our sewing machines and the Sidewinder does. This allows better and tighter feed onto the bobbin. I like it so much I bought three more and gave them as Christmas presents to some quilting friends. They absolutely love them. However, one friend has bought a Viking Diamond and the winder does not work with those bobbins.
Another option is to consider purchasing some prewound bobbins, I use NEB, which are would more densely. I think I paid around $40 for a gross of bobbins.
(The dealer I use is Ken's Sewing in Muscle Shoals, AL. www.kenssewingcenter.com)