I've held off on buying Garritan products for a while mostly because I began with other developer's libs and continued along their upgrade paths. However, Gary's JABB library was too much to resist so I picked it up since there's nothing out there like this jazz library, something I've been yearning for for years.
Now I can understand why so many GPO users rave about the performance features on Gary's products. They are really quite intuitive. I especially like how the mod wheel is assigned to volume rather than a slider. Ergonomically, the mod wheel is faster and smoother to my mind (er hands actually). Anyhow, having studied and played in jazz orchestras in my university days, I'm quite pleased with the sounds and the way one can manipulate them to evoke more realism in the lines. What a neat feature to be able to simulate legato with the sustain pedal!