Thanks for this! My dream Muni app would show the average time it's currently taking to get through the Market underground section (where I see most of the bottlenecks, esp. on the N). This is a good proxy in the meantime :)
The main issue is that until I go through and rewrite the whole thing to do long-polling for every line, it's expensive to compute each route since I have to make several requests to ProximoBus to get all the necessary data. Caching for five minutes helps, but it's still less than ideal.