Robert Schnur, adjunct taxation professor at UW Law School, told my class that once state's universally started statutorily approving LLCs, that he started cutting down his lecturing in his taxation courses on S corporations, pretty much to one class in a whole semester, solely because he believed that LLCs would pretty much crowd-out S corporations to oblivion. However, surprisingly to him, that has not occurred, and he has now stretched his teaching on the taxation of S corporations back out to the 2 weeks they had before. Lucky for me, I guess.
One more thing. Professor Schnur (I am not sure if that is the proper way to address him - oh well) told our class of a planning session he once had with a corporate client of his law firm, who was seeking to create a pass-through subsidiary (for whatever reason), and wanted his opinion on what form this new entity should be, considering the corporation's objectives. Professor Schnur gave his opinion that an LLC would clearly be the best form for this new entity - for both tax and non-tax reasons. The corporate client, however, decided otherwise. They chose an S corporation over Professor Schnur's misgivings, and stated that regardless of its pass-through taxation, limited liability properties, in their eyes, it was still too "new" of a creature for them to rely on. Professor Schnur suggested that this irrational apprehension might be shared by others in the corporate world (however, doubtful) and that maybe if there is more case law upholding its limited liability this may lead to more corporate embracement.
Maybe if I forward your above link (see "many other states") to Professor Schnur, he'll start reducing the emphasis on S corporations: at least on his final. It will save me from some additional reading this weekend.

Justin, Thanks for this comment. I have often heard this refrain from tax practitioners. It seems to me, however, that we are largely beyond the "LLCs are new" stage. At this point, inertia -- and some lingering differences in self-employment taxes -- might be the better explanation for the continued appeal of S Corporations.