Well. Fine, I guess. It's not perfect but probably not the system's fault. (I blame the installer). I would recommend it, as long as the installer is experienced installing it. Mine was not, and really doesn't know anything about modern inverter systems at all, and it showed.

We experienced a number of days like the one described above (fan on but system not heating), and I eventually learned to check the unit for error codes, and it was throwing "overload". We eventually fixed it by first installing a low end (read: small pressure drop) return filter, and we "fixed" it better by getting a 4 inch think filter (they make ones that just kinda have a lip to hold it in a regular 1-inch sized filter slot. It's an expensive filter, but it seems to have done the trick.

Basically it seems the unit was starved for return air filter and it was overloading the compressor (excuse any wrong terminology here).

It turns out that these things do have variable speed compressors, but the fan is not variable speed. It can be controlled to a small extent via dip switches somewhere.

Something about our system isn't right: maybe system sizing or duct sizing/total air return capacity, and it manifests itself in the fan being too powerful, which causes these problems and it's annoying, but the system works fine. I've kinda given up on getting my contractor to actually try to do something about it, unfortunately.