The striking difference in attitude between commercial users and open source users (e.g. more professionalism, gratitude and patience in the former than the latter) is most likely due to one of Cialdini's Influences: Commitment (in the book, "commitment and consistency").
It seems that the initial decision to spend money on software causes an emotional investment in the user. One would therefore expect that when a user has had the choice of software forced upon them (e.g. the use of Windows in a corporate environment, the use of an unfamiliar version control utility in a dev department, etc), they would be as impatient, rude, and generally unprofessional as a typical open source user.
Informal observation bears this out, but it would be nice to see some studies demonstrating the effects -- a simple review of ticketing systems for similar projects (Apache/IIS, Eclipse/VisualStudio, etc) should bear some fruit.