I didn't encounter any specific problems, though for later configurations (involving multiple lights), trying to setup the scene to exactly mimic the given rendering quickly became tedious. Instead of nudging a parameter, rendering, checking and repeating ad nauseum, I thought it might be easier/faster to do some of the "modeling" in an environment that allowed more real-time manipulation. To that end, I found a head model that closely resembled the given model, and setup scenes in 3ds max in which I could perform a much faster version of the "change parameter->render->check" loop above. An example of one such scene:
Once this scene was setup to my liking, it wasn't that difficult to convert from the parameters used in 3ds max to the corresponding ones for pbrt (simply keeping the proportions intact). 3ds max allows tweaking of every lighting parameter that pbrt can make use of so I didn't have to fabricate any from scratch.