I've seen knitting machines and I know a person who owns one, but I've never had any desire to use one. It comes down to the reason why I always loved knitting more than sewing (which I am really bad at). I love knowing that every stitch of the fabric of the piece of work I am doing is made by my hands.
When you think about it, when you are making something for someone you think about them while you are making it. It's a lot like the Scandanavian tradition of weaving one of the knitter's hairs into the fabric. It's an important sentimental significance and using a knitting machine would seem to negate all of that.
That's just me, though. YMMV.