First off: The premise of Calm is brilliant. Earth has been decimated by a fungus that causes stress to kill you. Like any proper post-apocalyptic game (a woefully underrepresented genre in IF), you have to act carefully to survive, but the survival process is based on avoiding stressful situations and finding ways to destress.
The descriptions are atmospheric and evocative; coupled with the smooth implementation, it's a rewarding world to just wander through.
There are, however, some issues that keep this good game from being a great game.
First, the player's mood is a two-axis scale described by a single adjective. While I must applaud the author's vocabulary, it left me constantly guessing. I would have preferred two quantitative values to one qualitative one, although I suspect other players may disagree.
Second, while multiple solutions and implicit actions are both good mechanics, I don't think they work that well in conjunction. The game allows various items to be used for various acts and automatically picks one of them if you don't specify. Since items are everywhere and there's no carrying capacity, most actions succeed without you really having to think about them. Again, some people may like this; I found it too Nemean-Lion-ish. Occasionally the games choices didn't make sense, either (smashing a lock with a bottle).
Third, the starting quests feel pointless to me. For instance, one requires you to gather food, but you never need the food, and you aren't penalized nor does the quest revert to incomplete if you eat all the food or drop it.
Still, it's a well-realized game and I found myself returning to it. My concerns may not bother other players at all. Calm is worth checking out.