Already basically covered by some other responses, but it depends greatly upon company culture which varies between industry and region. I can't speak to your

Already basically covered by some other responses, but it depends greatly upon company culture which varies between industry and region. I can't speak to your region at all as I've never worked in the midwest, but in a lot of places I have worked (which includes the east and west coasts), employees at pure software shops often have a negative view of anyone wearing a "suit", including to an interview. It isn't going to tank your chances with an otherwise good interview, but it can leave a negative first impression which is something that can snowball out of control on an interview if you aren't careful. If you're totally unsure for a given interview, a good rule of thumb is to ask about the expected dress up front and then dress a little bit better than what the answer is.