> Library management quirks aside, KiCad is...
I use it very, very rarely so really don't remember more than that.
Footprints and schematic symbols should belong to a parent component class with provisions for inventory tracking, etc. Their library manager works fine for hobby level work but if you're doing production you'll have to have a separate component management process that you integrate yourself.
What they have is fine, it works, but it's a far cry from what you get with siemens eda (mentor graphics) or altium.
My criticism is mainly that the PCB layout tools were still buggy. I believe it is/was using some of KiCad's router code, but it took more work to get a layout done than doing the same thing in KiCad would. It also tended to get glitchy with increasing layout complexity. The schematic editor is a lot slower than KiCad's and not as feature-rich.
The GTK widgets look and work very nicely on gnome-based environments but have issues on kde / windows. To be fair that's a GTK issue and not a Horizon issue, but unless Horizon has changed a lot lately I'd have a hard time recommending it over KiCad right now for professional use.
That said, anything using an HDI stackup or a reasonable number of differential or matched traces, KiCAD becomes a struggle. Even simple things like a single pair can be pretty tricky if you have space constraints. These features are pretty fundamental for modern PCB design.
It seems like KiCAD v6 will be making a lot of progress to manage more complex stackups and impedance control, so I'm very excited to try it.
Also check out realthunder's freecad fork, they've made some good progress on topological naming (with the effect of keeping models far more stable through minor changes). It's still unusable for all but the lightest duty professional work but it's an improvement.