Recurse Center alum here, and have overwhelmingly positive things to say about it. I'm sure there are lots of Recursers lurking here! If you're looking for more accounts, google "RC/Recurse Center return statement", the traditional title for an end-of-batch recap.
I'll stay this, too: Recurse is very communicative and transparent about what you get out of the experience. So, the website [1] is a good and honest resource to learn about them. As they promise, I grew a lot as a developer, met some fantastic and brilliant people, and now have a super valuable network to help me find jobs.
The thing that's hard to put into words is the personal growth you get out of self-directed learning. RC supports you through this, but deciding what you want to work on and finding your own path forward is a hard transition for many people (I hear you get a similar experience doing a PhD, not that you can compare a 3-month retreat to a 4-6 year program, of course). Some of my favorite moments at RC were hanging out late in the evening, talking philosophy, code, music, projects, research, life goals, you name it. It felt like the best parts of college condensed into a 3-month retreat.
Another thing to know is that RC is a YC startup, and (this is absolutely my opinion!) I think PG wanted RC to be for devs what YC is for makers. You're in a space of diverse, smart, passionate developers working "at the edge of their abilities". That's super motivating, in the same way that I imagine working on a startup in a YC batch is super motivating.
I don't mean to sound like I have rose-tinted glasses on. Parts of RC were hard, and finding 6-12 weeks to take off to attend can be difficult (though RC provides grants for underrepresented folks). I'm sure some people would have a better experience in more structured programs.
But yea, I had a great time. I learned Rust, bettered my React, prepped for interviews, and worked on a bucket-list project mapping songs in 3D space with three.js. And I made friends I see weekly to this day.
[1] https://recurse.com