What's a roguelite mechanic you thought you'd hate but ended up loving?

For us? Permanent Progression. We used to think it defeated the whole point of the genre, but then we thought - hey, why don't we just make them have 99 lives for their single save, and if they expend all lives, everything's lost forever?

There's permanent progression which we hate and love, but the more risky it becomes to actually lose all that perma progress, the more exhilirating every run in our game becomes. So what's yours?