I've done a couple of tracks featuring this instrument, and I'm still exploring it. As of the recently released version 3, it has the following features:
Up to 5 x independent round-robins per key, for each of the 5 strings of the banjo. Each string was sampled chromatically up to the 17th fret. The first string was sampled beyond the 17th fret.
All the strings are sampled on 5 different pluck positions of the banjo.
The Pluck Positions can either be selected via Key Switches or via a very advanced Pluck Position velocity selection system. You can freely adjust at what velocity level the different positions will be selected and make any kind of position combinations. All the settings can be saved as Presets.
The Bluegrass Banjo V3 also includes 379 MIDI files to help you build realistic banjo arpeggios and chords.
Banjo resonance via an Impulse Response made from the banjo head.
Various articulations: Hammer-On and Pull-Off, Half step and Whole step Slide, Harmonic and Scruggs D-Tuner bends. All with 2 x independent round-robin per key.
A very advanced and intelligent scripted Pitch Bend and Vibrato control.
Detailed KSP scripted control of Fretting Position on the neck of the banjo, including an Auto Fret Selection feature.
A Key Switch Page where you can freely assign which key will trigger the various Key Switches and save the settings as Presets.
8 different effects - each with its own Preset menus, so you can save and recall all the various parameters.
Bluegrass Banjo requires the full version of Kontakt (v4.2.4 or higher), not the Kontakt Player. It performs flawlessly in Kontakt v188.8.131.521.
If there's a better banjo virtual instrument, I haven't found it yet...and after using Bluegrass Banjo, I'm pretty sure I'm done looking.