1. The ultra-nok is heavy, has screws that could back out, IMO noiser, the constant metal to metal contact between release and ultra nock is bound to wear something out, and also more expensive.

2. No, never any trouble to get the release on, becomes second nature.

3. As was said, the more you shoot, the more the knots tighten. I have used just a loop with no brass or tied on nockpoints without any movement or slipping.

A string loop is just easier and more convienent to me. They're easy to tie, easy to replace, and easy to tune. You just cant go wrong with it.