We didn't know the AC company we chose didn't normally do them. They told us about it, sold us on it, and then royally screwed up the installation. We had them fix it a few times, then they had to basically replace all the inside heads. And even after that, they still aren't right. Some of it is simple incompetence, but some of it had to do with knowing how to install a minisplit in particular.
We're now paying another company to completely replace it, just 2-3 years later. The manufacturer's warranty is gone (Don't buy Lennox! 2 year warranty and garbage hardware!) and the free (warranty) labor from the AC company isn't worth the time and hassle.
If you want to save a little money, Daikin is almost as good and a little cheaper. Below that you’re rolling the dice on service calls.
If you're comfortable putting a hole in your house for the line and running power, it can really save a lot of money.
Insulation matters more with heat pumps, especially ceiling for cold starts (for descending heat build up from the top) as low temp air heating is not as radiative as IR from traditional heating appliances, or the conventional oil radiators that move air passively.
CO² heat pumps are less impacted due to the much higher air temperature but they are very uncommon for split system (dangerous), and usually used for water heating in AIO unit in a basement.
Had a house electrical failure recently with solar, ran one 18k BTU unit for 60m² on a tiny 5hp Diesel generator sipping 0.4L/hr. (2-4L for Diesel burner in comparison)
These models need proper installation as they use a synthetic proprietary lubricant compared to the commonly used mineral oil, moisture or contamination during tubing installation is a big deal for twin rotary compressors which may reduce service life.
HVAC companies push multiple mini-splits these days because they're faster to install, and have better margins, even though they're technically not the best solution versus centralized air.
Work fantastic in the summer, quiet, work really fast, and pull humidity out as well. In the winter they are great because they allow each room to be its own temp, key for pandemic months where my wife, son, and I all like specific temps.
I am very impressed with how little electricity they use!
Here's a pair of really great videos about heat pumps and what they can (and could, in the future) do:
For the summer, the heat pumps have replaced our terribly inefficient whole-house central AC. We have a PV solar electric system, so we can use the electricity we produce to run them, and once I started paying attention to energy use in our home it was clear that the old central AC had to go.
The modern mini-splits are pretty much maintenance-free, and are warrantied for 12 years. Best off all? The compressors are very quiet. You can have a normal conversation standing right next to them.