We've used Convertible multiple times in our current house; they installed our tankless water heater (with an unusual venting requirement) and the experience was so pleasant that we had them back again a year later to install our central air unit.
Most recently we noticed a gas smell in our utility room and Marnie had someone out the same day to locate the leak (on the original furnace supply line, notably not installed by Convertible) and patch it up right away.
What I've found the most refreshing is that of the 4 or 5 workers we've had from Convertible in our house every single one has been not only professional, friendly and prompt, but have gone out of their way to explain the work they've done to someone who knows a fair bit about computers but nothing about furnaces and water heaters.
When we move to our new house we know who we'll be calling if we need HVAC services...