For NYC anyway, the main weakness is the small base of trained artists. Then there's the fact that most of them are fairly senior TD-types who charge justifiably high rates, and are either overqualified for most artist-level assignments, or just not character animators since most of the Houdini artists I know are focused on FX and sim work (assuming that Houdini's character animation tools are in fact up to the job). Then there's the relatively high cost of Houdini itself, the lack of Arnold support, the steep learning curve that makes it hard to train anyone but a dedicated staff artist in Houdini...
Don't misunderstand -- it's an awesomely powerful tool in the right hands; I wish I had taken the time to learn it years ago. But just as I wouldn't want to run a woodshop that did all of its work using, say, CNC mills and lathes instead of hand tools, I wouldn't want to run a small commercial CG shop with just Houdini. I mean, you *could* do it, and the work could be done at awesome quality, but it would be pretty strange workflow at times and very expensive I think.
