I am a Hvac Contractor. This business (family owned)has been in business since 1956. I have been installing high efficiency furnaces since the 80’s. In the 80’s and 90’s I used to do warranty work for about 10 manufactures on tanks and boilers and furnaces. Number one rule 97% of all problems are installation. Second rule is that out of 100 units built 2 will fail. No manufacture builds a unit that wouldn’t heat your home but thousands of contractors out there can screw it up with out the training or knowledge. Yes 40 years ago units were simple, but I have found that the furnaces are more dependable now. But I sell Armstrong furnaces (99% are the 95% models) and I recommend these and promote them because of their dependability. I get my business from referrals and happy comfortable customer not the fact I sell Armstrong but because of the way they are built which helps my reputation. Did your service person check everything, gas pressure, manifold pressure, temperature rise, grounding, clock the unit to make sure it was proper. I have gone to check units that homeowners were unhappy with a product only to find that it was not installed or set up properly. There are to many out there just slapping these units in. One common problem on a condensing install is there is not enough slope on a side wall exhaust and no support so water will collect in the low spot and the unit will shut down if the pressure switch will not stay closed and turning the power switch off and on is not a repair. Blower motors burning out, are the ducts big enough? Was the unit over sized? If you had an old furnace that was 100.000 Btu’s (at 60% efficiency) you don’t put in a 100,000 high efficiency furnace you would put in a 60,000 btu at 95% the old 100,000 gave you 60,000 btu’s of heat the 60,000 hi-efficiency would give 57,000 btu’s of heat. So if you put in 100,000 new furnace it would del 30% more air so chances are the static pressure is too high and the motor would work too hard to try to get the volume of air to the outlets. There are lots of reasons homeowners would be unhappy and these are just a couple possibilities. Sorry for being so long winded but anybody wanting to check out a product google class action lawsuits (and the product type – e.g. runners, desk or whatever they are checking out) I really hope customers go with the contractor they are comfortable with, and if your gut tells you something, listen to it. Hope all are comfortable and happy from now on. Cheers!