I asked MM Comfort Systems for a bid to add a new heating duct in my house. I got a call 10 minutes before they were supposed to arrive in the morning saying that they wouldn't be able to make it.
Despite the last minute cancellation, I agreed to let them reschedule for next week. They arrived on time, and gave me a quote of $500 to add a new duct. They then charged me $100 for the quote.
I told them that there had been no mention that there would be a charge for the quote - and that neither of the other two companies who had given me an estimate had charged me for it. The technicion insisted on payment, so I made it. I sent a letter informing the owner of my experience, it was ignored.
I decided to go with Bob's heating and air conditioning based on the comments in this book. Their quote was only $350.