I watched a friend stream a good amount of it (since I no longer live in the sticks and streaming video for a few hours is something I can do now, it's exciting) but pulled out because I wanted to play it myself and leave stones unturned. The soundtrack is really great, I've had Papyrus' battle theme in my head since then.
It's gotten me thinking about pacifism in games. Specifically... how should a game go about presenting pacifistic options without making it feel like pacifism is playing the game right and violence is cutting the gordian knot? In Undertale, because how to end battles nonviolently is explained and more elaborate than fighting, it feels like it's what you're supposed to do. Maybe because we just can't really think about a game that has multiple endings, but doesn't having a "true" ending and an intended way to get it. Maybe it does have more to do with the player's actual real-world moral compass and all it takes to make an enemy difficult to want to kill is to make it relatable. Maybe consequence is necessary, but it's impossible to have consequences that matter less to the player than simply being good.
I want to think there is a perfect way to present choices like this in games without making them explicit, and resulting in most players going good because that's what they would do in real life.
ANYWAY, Undertale cool and interesting. A bit heavy-handed but still smart. Soundtrack good. Characters fun. World mysterious.