So I tested out this little machine last night. I was surprised that it felt sturdy, despite it being so light. When stitching there was a very solid feel, which made me thing it probably could easily handle some heavier fabrics (though I didn't test that). The stitches were nice, I didn't have too much trouble setting it up. But I knew pretty quickly that this was not a machine for me, even as a back up.
While I did get it threaded, the fact that the hook race was buried back in the machine so you can't see much of it, even when in the highest position, makes it difficult to be sure you have connected with it. It was fiddly getting the thread behind the little bar above the needle. I did manage to get the threader to work after a few tries. I did like the bobbin set up, and that I did not need to pull up the bobbin thread. I got a bobbin wound easily.
If all I wanted it for was a back up for piecing, I might have considered keeping it. But I am also into sewing. I didn't like how the line markings were at the back of the needle plate and not carried over onto the front, which makes it a bit more difficult when starting a seam to know you are on the line (unless you want to start 1/2", give or take, from the edge of the fabric so that you can line your fabric up). Also, I like to work with knits, which I use a zig zag stitch. I could only go down to 1.5 on the width (I prefer 1.0). The resulting stitch was actually kind of pretty, seemed like a pretty scallop almost. But that isn't what I always want when top stitching. Lastly I noticed that the needle plate area was slightly raised from the bed of the machine. Were I to try free motion quilting something small, I think that would be bothersome. Probably bothersome in other instances as well.
Lastly, it doesn't have a thread cutter (yes, I knew that before I picked it up). If I had like the machine otherwise, I could let that feature go. But having other qualms, I'm not willing to give that up as well (yes, I guess that makes me spoiled).
Those were my impressions, in case anyone else is searching for reviews on a Costco machine. I do think it would probably be a good little machine, but I also think I am looking for something else.