The Old School Renaissance, Old School Revival, or OSR, is a play style movement in tabletop role-playing games which draws inspiration from the earliest days of tabletop RPGs in the 1970s, especially Dungeons & Dragons. It consists of a loose network or community of gamers and game designers who share an interest in a certain style of play and set of game design principles.
I have enjoyed a few games of Troika! and Electric Bastionland, though by their own nature they're hardly long-campaign focused titles, so I wouldn't say I have much experience.
Its good for chaotic, high-risk, low-regrets sessions
I ran a group of players through a DCC funnel this year and had a great time! Though I think we might switch to The Black Hack moving forward, just for ease of play.