I'm from out of town - state - and country. I've been to Club Passim a few times but only for specific shows so I haven't been able to explore the venue to its full extent. However, I've been to it enough that I can understand its seeming legendary status.
It has a great community vibe. Of the few times I've been, there are people I recognize from previous visits. Something like that is important for a place like this and also likely hard to attain so that's definitely a plus. It's also a great performing venue - at least from a spectator perspective. There have been shows there that I've wanted to go to but couldn't (due to my being from so far away) but the shows I have seen have always been excellent.
The downsides? It's cramped and tight. Good when it comes to watching performers but it's easy to get interrupted when drinks are being ordered and delivered. It's a tight squeeze. Other than that, I do look forward to coming here any time I'm in town.