I’ve avoided commenting on the Simpsons/Springfield hubbub since radio, TV, the newspaper, the internet and several local blogs have covered it quite nicely. There are lots of arguments in favor of our Springfield being the Simpsons’ Springfield. Some are kind of lame (like the Simpsons’ elementary school looking like Springfield High; they both have traditional school building appearances along with 5000 other schools across the land). Others are kind of compelling (like the Springfields’ proximity to a Shelbyville).
It seems to me, however, that there is one bit of evidence that would pretty much preclude our Springfield from being THAT Springfield. The Simpsons’ city is not the capital of the state in which they live. I recall an episode from maybe a dozen years ago where Homer became a the mascot for the Capital City baseball team. Capital City was some distance from Springfield in that show. And if there is anything (other than Abe) our Springfield is known for, it's being the state capital.
Disclaimer: My Simpsons trivia is a bit dated since I haven’t been a regular viewer in ten years. I was an avid viewer the first six seasons or so but after that I couldn’t tell you much about what has gone on in the show.