Convertible installed a new high-efficiency furnace and a new tankless water heater (gas) a few weeks ago, and it was overall a very positive experience.
I had a few companies give me estimates, but I went with Convertible because of how Mike, the sales rep, was very clear and straightforward with my options. He laid out what he thought my house needed without trying to push only the most expensive options.
On the day of the installation, the guys were very polite and clean. I live in an older semi with a shared driveway, and so it took some careful planning to figure out where to vent both the furnace and the tankless. The installers gave me a few different options and showed me exactly what each would look like before they started, which was very helpful. They also made sure to seal up the old furnace vent (through a chimney) with foam so that cold air could not get back down, which I appreciated.
So far, the tankless has been working great, but I have not yet had to use the furnace. I have used also Convertible in the past for my air conditioner and for servicing, and I recommend them to others.