I had someone from Boehmer come out to my house in the Fall of 2016 to look over our heating/cooling system, since we had been in the house for about a year but hadn't done any maintenance on our HVAC system yet.
From the moment the guy arrived, it was pretty apparent that he was trying to upsell us hard and thought I didn't know squat about HVAC stuff (which, to be fair, is true, but still...). He took a quick look at our outdoor A/C unit and quickly insulted it and couldn't believe it was still running (it's still running fine as of Spring 2018). He pretty much had the same reaction to our furnace (i.e. "this is a POS").
He poked around in the furnace a bit and then proclaimed that the heat exchanger was rusted to the point that it needed to be replaced, and that would be about $1250.
I was immediately skeptical and did some internet research. While a cracked heat exchanger is a serious issue, simply the fact that it is rusted does nothing to indicate that it's cracked or needs to be replaced. I got some new CO detectors so we didn't die and just left it alone. It's been fine since.
On top of all that, he left mud tracks in our kitchen when he came upstairs after doing his "inspection" and was completely oblivious to this and didn't apologize.
I had to get the blower motor replaced in the furnace in early 2018, but other than that, the furnace has still been going strong.
TL;DR: Bad.