I adore this machine. XD I wanted to wait a while until I had plenty of experience with it before writing this review, and I'm still just about as happy with it as I was the day I bought it.
I have used it extensively on a regular serging stitch as well as a rolled hem. I have not used the gathering function yet.
Much of what I have done with this machine is to finish off seams so I can sew without worry of fraying and to have a more professional finish. I have also used it with wooly nylon on nursing pads and baby blankets, to have a soft edge without any loose threads.
The rolled hem is beautiful and even, and it's very easy to make the change. You take out the left needle. Then you open the front, rotate the knife down (I don't know the proper terms for the parts yet...), and use the other handle on the left side of the machine to push the inner knife out of the way, then you pull down the pink handle from S (serge) to R (rolled). This pulls the stitch finger out of the way. I usually put the knife back in place afterwards, but I really don't recall off hand if you're supposed to do that on a rolled hem.........
Definitely keep your manual within easy reach. Sometimes you think you remember how to set it up/back to normal/change the stitch, but there is often a tiny thing you forget.
I know the conventional directions for threading tell you to thread upper looper, lower looper, left needle, right needle, but I find it easier to thread this machine from right to left. So I usually thread it lower looper, upper looper, right needle, left needle. If I try to thread it the other way, it often won't work quite right. On the one hand, I wouldn't necessarily say this machine is simple to thread, because the lower looper can be challenging. However, by the same token, I managed to properly thread this machine the very first time I pulled it out of the box. I don't usually re thread from scratch; I typically tie off on the loopers and cut the needle threads, then serge a tail, then thread the needles after the old thread runs through them. Nonetheless, it isn't a huge problem or annoyance to me if I end up having to thread from scratch, because the color coding and the diagrams inside the machine help keep things simple. :)
Sometimes I have trouble getting the feed correct when I am serging. It will stretch or gather the fabric a little bit. That's mostly my own fault for serging without testing on other fabric first though!