Quite a lot apparently!
The feedback from the people I do business with, contacts on Twitter and from my friends was surprisingly consistent.
A "freebie" address such as Hotmail, GMail or Yahoo is considered ok for start ups and sole traders - but only as a means of contact. People are generally very reluctant to part with cash if no other dialogue occurs. Not to mention that most online payment services won't accept subscriptions from a "floating" account. The reaction is somewhat ameliorated if they know the person, but there is still the perception that they need to get a "proper" email address.
Almost equal wariness was accorded to businesses only using their ISP providers email. Again the understanding was there that this was ok within strictly defined limits. However, people were more inclined to "trust" these addresses more than the floaters.
Another consistent reaction was mild annoyance when companies have a website, but use a different domain name for their email addresses. The most common response I received when I asked for a reason was that it was "lazy".
However, the strongest negative reaction I got, across the board, was not to what appears on the right hand side of the address - it was the "name" that could really rile people!
Top 5 most despised:
You have been warned...