A big advantage of knitting a sweater from the top down is that you can try it on as you knit.

Like so:

I spent a good part of the day knitting the ribbing on the cuff.

When I got to what seemed like wrist-length, I bound off the sleeve.

And got this:

I’m not thrilled with the edge of that sleeve.  I’ll probably frog all that ribbing and do something else later.  (Oh!  Maybe bracelet-length sleeves with a crocheted edge?)  In the meantime, I’m going to start the second arm.  I’m pretty sure a couple of my neighbors were wondering what I was doing out on the porch, taking selfies in what appeared to be a one-armed sweater.