McKinnon installed my furnace several years ago - was quite satisfied with their price and service, but they didn't have the AC brand I wanted (Lennox) when I replaced my AC about 3 years ago, so went with another installer.
AC wasn't cooling properly this season, so contacted the original installer (a different company), who sent out a tech 3 times, who only proceeded to charge it up. The 3rd visit, I didn't even see their tech on site and got a call from a unknowledgeable customer service rep that I needed a new coil that would take a month to get.
After over a month, I called McKinnon to come and take a look - their tech was extremely thorough and tore everything apart trying to diagnose the issue...something the other company should have done. Turns out, when installed (by the other company), they did not install a part required to maintain differential pressure. Part installed and AC has worked perfectly ever since.
I've been happy in all the interactions I've had with McKinnon and if not for my preference for the AC brand, would have had them install it as well. I intend to use them for all future servicing.