I liked the mist at first. It's a really neat concept. But every other biome, the gear you acquire over time slowly makes that biome go from oppressive to chill.
The mist never becomes less oppressive. It remains the exact same problem that it is from the moment you set foot through the fog wall with a wisp light out. It clears so slowly, and in such a small radius. Wisp torches barely clear out anything, considering the resources you need. Several night's worth of wisps and several shoots worth of wood and you'd barely clear enough mist for a tiny outpost. Not to mention their lack of vertical reach.
The verticality is interesting. But hit detection is really bad when attacking from different elevations. And fighting an enemy that doesn't slide on slopes and doesn't have a stamina bar, while you're sliding every time you stop to attack, and managing stamina not just from the fight, but also just trying to maintain a position, starts to get really tedious and annoying, and that negativity gets compounded by the poor hit detection.
There's a lot of interesting stuff here, but it's overshadowed by poorly implemented mechanics. Any other biome I can hang out in all day. Mistlands starts to press some bad buttons in my brain after a while and makes me want to do anything else just to get away from the mist and constant sliding.
Source: https://www.reddit.com/r/valheim/comments/108ast6/mistlands_arent_enjoyable_after_progressing/