Is there a caveat to using drivers on node properties? So, it seems to be a trivial matter to use a different seed on each frame (it looks nicer in animations). I.e. type "#frame" into the seed value and viola! You now have a driver. In fact, if I turn on "auto-run python scripts," it even updates interactively.

HOWEVER, this appears not to work in the node editor. I have a texture that I'd like to animate (by driving the location in the mapping node), but the driver I've added doesn't get updated; neither interactively, nor even when I render. It will update each time I open Blender, but never again.

Anything I'm missing? Or does this just not work?
If you want the driver on the mapping node to work correctly you need to add it via the outliner, not the node editor as you might expect.

See this tutorial http://vimeo.com/40389198 starting at ~18:30 for directions on how to make it work.

It don't know if this is considered a bug but the behavior certainly isn't very user friendly.