The KA attachment is absolutely fine as a small-batch grinder. It's not fast, but if you're doing 5# batches it's perfectly acceptable... you'll spend more time setting up and cleaning up than actually grinding no matter what grinder you use. Bigger batches will have you wanting a dedicated grinder.
The KA attachment is horrible
as a stuffer, though. I mean really, really bad.
EDIT: In response to the above post, you can use loin, but it would be a waste of a good, relatively expensive cut (even if you got a deal on it), and you'd need to add at least 25% fat to it because the loin is one of the leanest cuts you can get. I'd butterfly that bad boy and stuff it with rosemary and garlic per Steven's recipe.
Stick with butts for sausage... they have almost the perfect amount of fat to lean and they are cheap. You can't go wrong.