Check out the video. In the example, rendering of an animated model goes from 0.25fps without it, to 4fps with it using CPU rendering, or up to 40fps using CUDA for the example model....

I'd say that is large enough to have the potential to fundamentally alter how people work.

"fundamental" seems to imply a magnitude shift. 100x seems the minimum bar IMHO. Otherwise its just decimate..

In this case the frame rate went from 0.25 fps to 40 fps, a 160x improvement, so "fundamental" it is.

Also, diminishing returns apply: going from 0.25 fps to 40 fps is a game changer when doing interactive modelling, in the sense that only one of the two can be considered interactive. Going 40 fps to 4000 fps wouldn't really be make things much better (I'm sure artists would simply push the tools to bring that frame rate down again, and any improvement to render speed obviously would matter for final exports, but you get what I mean).

Kind of - it depends on the artist you talk to. OpenSubdiv utilities have been part of the major 3D packages for about a year or two now, and it's true that they can offer some significant speedup, well-needed in both the games and per-rendered CGI industries where high-poly subd models can easily go up to several million triangles.

Besides the speedup, there is a very interesting feature of OpenSubdiv - local edge creasing. To influence the general creasing or smoothing of a subd mesh, an artist usually has to add more or subtract geometry in an area, respectively - whereas OpenSubdiv gives you the alternative option to assign a crease value to an area of the source mesh which influences the apparent creasing of the resultant mesh in that area without the artist having to add more geo. It works some of the time: not every artist likes using local edge creases but for those that do, it can be a very big help, considering the the occasional difficulty in adding new geometry to a mesh that flows correctly and doesn't accidentally ruin the rest of the mesh.

I'd say a 1-2 order of magnitude speedup is very significant.