Just a fast one, can Houdini use something else for skininng besides bones and metaballs? Nulls perhaps? If metaballs are used for facial rigging/skinning, how big impact they (metaballs) have on performances of fps and speed of overall rig? Are they "choking" viewports?

Ok, since nobody seems never ever tried this before, bones it is, now, how would you extract world position of nurbs CV's and use them to drive bones?

You can use any object as long as it has Capture Region SOP as those are essentially whats used in bones also

But nowadays I'd suggest you using KineFX as that's built around the idea that joints are represented as points and bones as lines, so technically it will be straightforward to use CVs of your nurbs curve if you resample it and ensure correct transform attributes are present

Oookaaay, I need to clear things up a bit... It's about facial rigging, the idea is to have nurbs curves with bones (or other objects whatever)attached to their CV's in world space (properly/uniformly oriented), and to drive nurbs deformations trough morphs (extreme poses) so the nurbs act like facial muscles, and in the end to balance those combinations of morphs trough the "joystick" (i.e. a circle shape in the box shape, limited not to abandon boundaries of the box shape, with the value of 0 to 1). I've done this many times, in Max or Maya... in Maya you would go to node editor and connect CV's WorldPositions to joints position... where do I need to go in Houdini to achieve this... maybe Chops? How would a network look like for one CV and one bone?