I've done a good bit of internet research recently and I've seen about zero examples of Norfolk Island Pine as a singular bonsai that looked very good. The one noted and pictured above is the best singular tree that I've seen yet.
However, I think that they can look reasonable and pleasing in a forest group. Their growth habit may be annoyingly top-heavy and/or somewhat difficult but they may have merit for some people since Norfolk Island Pine is perhaps the one conifer that can realistically be grown indoors successfully. I'm not convinced that they are truly terrible material, yet. I can't help thinking that all the mallsai pro-nanas destined to die a dry death indoors, residing over their little "Inspire" or "Peace" rocks, would be better replaced instead by Norfolk Island Pines that actually have a chance of surviving.