I have a threaded frame in the queue, unless I change my mind. Threadless has a lot of small advantages. The one disadvantage is vertical adjustment. For fear of jinxing myself, I've never had a quill stem get stuck, but I have seen it happen. But it takes a lot more care to prepare a threaded fork in the first place. I've recently seen someone searching for a headset with less stack height because all of the easily available ones didn't fit his threaded steerer.