I had used Diamond for a few years after originally having become dissatisfied with three other heating and cooling companies in town. I was always been extremely pleased with the maintenance work by John (the service tech), and Diamond in general for always wanting to meet or exceed my expections. So when my furnance eventually failed and the repair costs were high, I didn't hesitate at all to let Diamond upgrade it, forgoing even letting other companies provide estimates, as I was confident that Diamond would give me a fair deal with excellent installation and post-installation support. After telling Rob (the sales person) my requirements (low continuous fan speed/noise in particular), they installed a new unit that, because of recent changes by the manufacturer, turned out not provide the low noise continuous fan mode that I expected and wanted. Rick was able to find an upgraded last year's model, and he offered to install it for simply the difference in furnace cost between that and the first one, forgoing the charges for the additional labor to take out the current one and install the new one. And even when it turned out that it cost extra to actually have the new one shipped, Rick did not pass that cost on to me. In fact, when it was all done, to make sure I was happy, he even offered to make the swap for no additional cost, an amazingly generous offer that, despite not feeling comfortable accepting, was still unexpected and unlikely to have been given by any other shop in town. Consequently, I will continue to use Diamond, and while I don't usually recommend many other companies to my friends, I will not hesitate to do so for these folks!