this may be the back side but it's what i did with my circular attachment to my Janome.

Save money and just tape a regular thumb tack, point up, 1/2 distance from needle will make a circle twice that size and you can use any decorative stitch you want to. Use several strips f tape to prevent the tack from slipping. Play with it, you will be a mazed what all you can do.

First, I want to say what a wonderful resource youtube is,this is a great video... I am going to go do some round ribbon on a crazy quilt!
I have one of these circle attachments and it came with my Bernina, yes I have used it on several occasions and I like it... but if it had not come with my machine I don't know that I would have made the additional purchase.
I actually used this to create some circle appliques... use the attachment to tack down a piece of fabric, cut the extra fabric, now restitch with a decorative stitch.
easy peasy...

I originally thought of using it to quilt circles on a quilt like I've seen others do. just a regular stitch. But I haven't done that yet. not fond of poking holes in my quilt and the quilt going through the throat of my machine could make it come off of the tack if I wasn't careful.
doing blocks like this with decorative stitches and then putting them together as a QAYG would work fine though.

I have one for my Janome 3600 and it was invaluable making flannel nursing pads for my daughter. I used 3 layers of white flannelette, cut a square bigger than the size I wanted to make and used an embroidery scallop stitch in a circle the size I wanted. Then I trimmed around the scalloped edge with small scissors. My daughter loved them, they were easy to toss into the wash, they were absorbent, and it saved using disposables.

that scallop stitch, nativetexan, is the one I used with my circular attachment to make washable nursing pads (3 layers of flannel)

I have one for my Bernina, don't use it much tho.

For the drunkard's path I'm working on - I use a cut-away stabilizer and trim out the stabilizer "after" I turn and applique the circle on and cut in the 4 blocks. You could also use wash-away stabilizer "after" the sew down.

As for having to use stiffer stabilizer, that's not really necessary. I help guide the fabric around simply by having my hand just under the fabric to keep it level and moving freely.

I'm not sure how often I'd use circles but I'd like the option to. I would probably buy the flower one first to see how I liked that and if I found I used it often enough then I'd buy the more expensive kind which seems to offer a bigger variety of styles and sizes.

My next big purchase this week is going to be an ipad.:o