Yeah.. I have one.. It made a big improvement from the old battered ATM11 we were using with the band for accordion. The only other comparisions I have made is with a MC012 on an accoustic semibassguitar. I had no time playing around, but I found the NT3 to be less detailed than the MC012.
I also had it up against the NT1 on vocals once. The NT1 sounded better then, but now I wish I could redo it, cause the NT1 left me with all these ugly sibilants. Now I use the MC012 for vocals... It kicked the living daylight out of the NT1 with that singer.
I haven't compared the NT3 to other mics much otherwise, and I won't make any statements about its' soundquality since I don't have enough experience to do so. I guess I could do a little NT3 - MC012 shootout on vocals, acc-guitar and piano, but I'd rather see some old fart like Ed or Bruce do it..