I think somewhere in the middle is good. Not so uncommon that people get confused about pronunciation or spelling (that REALLY sucks!), yet still something a bit different that you are not hearing the name everywhere. Actually in my opinion, short length of name (or failing that, the ability to easily have it shortened) is more important than how common/uncommon it is.
As an example, I like the name 'Nathan' because it's common enough that people know it, yet it's not heard everywhere like some names, it's short (and could even be shortened further to 'Nate'.)