Had a group lesson on Sat. on the 12000. I learned a couple of small things I didn't know (and should have known) that were really helpful to me.
When replacing a snap on presser foot, you can push the presser foot up-and-down button and then the mechanical presser foot lifter can be put up and down. I was just clunking the machine down onto the presser foot by pushing the button and I knew that didn't seem right, but I couldn't figure out how to lower the mechanical one. The trick is that you have to push the up-down button 1st. And most of the people in the class didn't know that either.
On the bed of the machine there are a lot of useful lines. One line which goes all the way across, shows exactly where the needle is. So it is a good line to line up your fabric with when beginning to sew. Since you can begin sewing without lowering the presser foot 1st, it is a really good way to see that your fabric is in the right place.
Farther to the front by the little plate you take off to change the bobbin there is a line indicating a 1/4" seam. I noticed that when using the 1/4" foot that the 1/4" line doesn't make the fabric exactly line up with the edge of the guide. The instructor said you shouldn't be lining up your fabric exactly against the guide anyway. SO if you like to line your fabric up exactly against the guide and you want to get a scant 1/4" seam, when using the Quilting Stitch that says 1/4" patchwork you need to move your needle to the right a click or two.
There are also guides for I think 1/8" and 3/8" and for 45 degree angles.
Also on both 1/4" feet there is a mark on the foot 1/4" from the front edge of the fabric for when you want to turn a corner. I think most 1/4" feet have these but I had forgotten about it.