Loosening the bolt and tightening it again is not a problem by itself. What becomes a problem is that it's easy no adjust your headset too tightly or too loose, especially if you're not too mechanically inclined.

The NVO system can essentially be duplicated by installing a collar or a second lower stem at the top of the stack and keeping that one tight all the time. Then the upper one may be moved around as you wish without having to readjust the headset.