Hans Weilenmann & Bruce Salzburg did a long article comparing vises in FlyFisherman last year. It's the best article I've seen for comparison shopping, since no shop I've been to has carried more than half a dozen models. Here's the link:
As you will see, they think the NorVise, while good from a rotary standpoint, has some drawbacks. And, if you're going to be tying lots of small (<#18) flies, I think you'd want to have somebody show you (prove to you) that it's a suitable vise.
Personally, I don't know too much about the NorVise as I've been getting along with my Regal for a long time now (it's a vise with some well-known strengths and weaknesses I won't bore you with) and don't plan to switch. A.K. Best said somewhere that a tier should only have to buy one good vise in his lifetime. Seems reasonable to me.