+1 on the suggestion for a writeup.
Actually, the chaotic bit is on the currency exchange end. It seems to drive the rest of the growth process, which is quite a bit more orderly. System growth only looks chaotic because of this driver, but once you realize that there is extremely tight coupling between price and Difficulty the rest starts to fall into place.
I'm not sure I'd qualify the coupling between price and difficulty as "extremely tight". That's the question I'm trying to answer with my price over difficulty charts, but since there's only about six months of reasonable data available, its hard to know from which scale to view them. Zoom out enough and the ratio looks smooth, but zooming in there's plenty of variation. They are certainly coupled to some extent, which is good to know.
That is a good point, and it is probably a necessary refinement to the model, but that is actually a little more complicated to project since there is not a very reliable record of network hashing capacity, which is itself only arrived at in a derivative manner. It is statistically possible using high resolution data to estimate fairly accurately, but that fruit hangs a little higher than the easy to get, once per re-targeting period data I have been using... I suppose a reasonable analog could be arrived at just using the change in average time to solve a block between re-targets. I will think about it when I have more time.
blockexplorer.com has a netHashPerSecond calculation to a maximum resolution of every five blocks: http://blockexplorer.com/q/nethash/5
Very choppy at that high of a resolution though. Replace the 5 with any higher number for lower resolutions..