We had to do some extra work, but the customer service was fine.
When Ferrari Plumbing came out to replace our hot water heater they had to do additional work because there was a difference in height between the two units. Because of the extra work it was also more expensive. I was a little disappointed because of that, but there was nothing we could do. That had more to do with the manufacturer and the change of standards than Ferrari Plumbing.
As far of customer service they were fine. The guy they sent out was very professional and answered all my questions. He made sure I understood what the extra work was and why we were doing it. It really wasn't that much more money, I just wish it didn't have to be that way. Since they did the work we have noticed that on the hot end of the water it is hotter than it used to be. This is nice because we get more efficient heating.