Mitsubishi Mr. Slim opinions

I am adding a 30x16 family room addition and 20x20 master bedroom suite.
We keep our bedroom very cool, even in Winter, but prefer a warmer family/tv room. We are in Ohio, so winter can get cold and I understand that heat pumps are not effective at 18 degrees or less, so my thought was to supplement with a vent free gas fireplace for colder days (99% effficient). Essentially we are adding two "zones" to heat/cool, with each zone having it's own independent unit. has anyone had experience with the Mr. Slim products, and has it been favorable?

Good product

There are some byproducts from combustion with a vent-free unit. It consumes O2, and produces CO2 and H2O, with various other gasses, depending on how clean it burns and the exact composition of the gas feeding it. In a tight house, it's not the greatest thing. A small one for atmosphere that doesn't run forever is another thing.

In your climate, heat pumps are of limited use, and most installations of a heat pump would have back up electric strip heat, which is not an option with the minis.

I would consider some heat sources ( other that ventless gas....don't like that idea at all!)