10.5 Leopard was my peak. 10.6 Snow Leopard improved on its stability but had a touch of visible regretion (in my opinion). After that, I haven't really been happy with any release. Obviously some things have improved but... 10.5 was branded Unix, the UI was beautiful. It felt solid.

> macOS 15 is the last usable release.

Same. Will sell my Air when security updates stop for Sequoia