KirstenLee has posted an announcement about the release of a new version of the viewer: S19 (407). See: What dreams may come! In this post KirstenLee explains why version S19 is being used. Basically because this is the version of the viewer KirstenLee likes working with and using.
This is not a cutting edge viewer. Basically it is a V1 viewer being adapted to V3 three features and recent SL system changes. It is easy on hardware. So, I would class it as being in the same field as Singularity and Cool VL Viewer; V1 interface viewers.
I am not digging into the code so I can’t say it is behind, equal to, or ahead of the others. Nor is there any way for me to know the time being put into the viewer.
With the new features coming from Linden Lab, I think this viewer will continue to fall behind. But, it appears KirstenLee will be updating the viewer as time and mood suits. Henri, the mover behind Cool VL, has shown it is possible to keep up and pass the Lab’s code pace. So, KirstenLee may do the same. Avoid speculating and try it for yourself.
I see this as another niche viewer for those that like the V1 interface.