I only play on LAN, so I can even set up as much instances as I like with a single CD-key \o/
(still, I bought the game several times, so I probably have a couple valid CD-keys lying somewhere…)

Here Iʼve only played it on Linux for years ;)
But LAN play between Linux and Windows clients worked well last time I gave it a try, as long as everyone is on the same version (1.13d in my case).

The only thing Iʼm missing by not playing on Battle.net are the ladder-only runic words, but I think I remember a mod adding these in the solo and LAN modes.

I started playing solo because all my friends moved on like 15 years ago, and I got back into it a couple of years ago. Runewords are nice but not needed unless you're speed running.

The game STILL feels more balanced than Diablo 3, but it might be nostalgia speaking.

Fair point :)