Yeah, your explanations helped me understand why it is the way it is.. I realize SketchUp does a lot "under the hood" in order to make it as useable as it is, so programatically adding a ton of points can be slow.. Obviously if I was manually drawing the faces in, it would likely be mostly unnoticeable. I do find it intersting though, that at a certain point it really does just hang, which makes me think even if I was interactively modeling, adding a singel face would be noticeable slow.. I can't believe that would be the case though. Luckily, I'm usually dealing with low facet count models, at least when I build them myself..
At any rate, I did download 2014 this morning.. After finally figuring out where my plugins were supposed to go (very different place than in SU8), I was able to verify that the grouping inside the loop with a call ro fill_from_mesh each time still acts the same way.. It seems to get through to about the 8000'th one (which is actually 16,000 faces for what I'm doing) and then it just stopped making progress, so I finally just killed it..
Like I said, though, the single-big-group approach will suffice for now, just isn't as ideal as the many group approach would be, so I'm happy for now.. Thanks!