I wonder if this increased responsed time is uniform across all tags. I work on ML implementations (SML/NJ and Manticore), and I've basically given up on answering questions on SO because every time I go there every question has been answered within a few hours. Even the difficult questions, and -- especially on SML/NJ -- often by people with no relationship to the implementation team who have clearly spent serious time spleunking the depths of our source tree to answer it.

Hard to tell without some statistical data. My tags may also be odd because I suspect our user base is skewed towards a mass of novices (intro to CS students) and a small number of experts, with very few people in the middle.