Hi Ced,

> You wrote "...Actually what I'm looking for is a replacement for T-Splines 4 which is no longer being supported for Rhino - and I depend on that for organic shapes. "

If that is your main need then I strongly suggest you to move to Autodesk Fusion 360 that include also T-SPlines.
Fusion 360 for the moment is free for hobbyist/enthusiasts.

> You wrote "...2-3 years between versions seems a bit long - and v3 has been out for several years..."

I disagree with you.
What really matters speaking about software in general and 3D modeler in particular is not the frequency of the upgrades,
but the overall consistency and quality and the more or less streamlined workflow of that particular software.
Also, speaking about 3D Nurbs modeler, there are only a very limited set of main commands/features.
It's mainly on that commands/features that is based the real quality and the "perceived" quality of a NURBS modeler.

And, from this point of view, IMHO Moi is second to none.

Best,

- Marco (mkdm)