I still play it when I'm looking to kill some time. It's held up pretty well. There's an active modding community, which has produced (and maintains) Heroes 3 HD.
Heroes 3 HD is a really cool addition that scales the resolution, offers some balance patches, etc. It also lets you install the fan-made Horn Of The Abyss mod that offers a new faction (Cove), new maps, and some miscellaneous tweaks.
I come back to it occasionally. I'm no longer interested in an extremely slow grindy turn-based game, but it turns out that the game isn't actually all that slowly paced and games taking 12 hours when I was a kid was just because of how I played it. IMO the gameplay never feels dated and it's still a candidate for the best game in the series.
Visually it benefits a lot from being at the very end of the 2d era rather than the start of the 3d area. The HD patch makes it work at modern screen resolutions, and as long as you don't mind pixel art it's really quite good looking.
Heroes 3 HD is a really cool addition that scales the resolution, offers some balance patches, etc. It also lets you install the fan-made Horn Of The Abyss mod that offers a new faction (Cove), new maps, and some miscellaneous tweaks.