Nice writeup, I wish I had something like that to peek at last week when I started playing with Julia/JuMP. However, I am now leaning towards using Named Arrays instead of Dicts for model parameters and variables. I posted some benchmarks here and found that Named Arrays performed significantly better. Dicts are probably fast enough though in most cases unless your optimization model is huge. But since I also build simulation models which do a lot of iterated assignments I wanted the extra speed.