I had Brent Air Systems replace an ignitor on my furnace that had broken which meant the furnace wasn't pumping out heat, only cold air. Of course, the furnace breaks on a cold day but fortunately these guys showed up within 2 hours after the call and the furnace was up and running about an hour after that. Very quick service, explained everything and also spent some time talking to me about what had broken (the ignitor) and explained a few other aspects of the furnace.
Side note: after I had this work done, I had an unrelated issue with my furnace so when I called Brent to enquire about help, they actually diagnosed the problem over the phone and helped me fix the issue myself, saving myself at least $120. They knew it was a minor job (some minor maintenance and cleaning that was required) and that I'd probably be capable of fixing it myself and that's exactly what happened. Thanks guys!