I'm thinking about getting straight stitch only machine and something like this comes with it. http://cgi.ebay.com/WHITE-sewing-mac...#ht_2713wt_976

How does it operate and is it easy to use??

I'm not familiar with this machine but many old machines had cams to give you decorative stitches. Maybe this attachment replaces the cams?

I'm not familiar with that attachment either. However, it looks like it is supposed to add stitches to your machine.

After looking at the picture on eBay it is my opinion that is a very early attachment to make decorative stitches.
It probably came with a set of cams.
I also believe it is brand specific and might not work on a machine it was not made for. Even at $9.99 it might not be useful. A low end machine with decorative stitches will do the same thing. The early Singer machines (1950's) worked ok but the system for cams was built into the machine.

It's a White machine and the attachment is White and comes with it. So, it must work. I just have never seen it before! I don't need or want the extra stitches, though.