Mine’s in a mid-sized 16U system. It’s always my end of chain mixer and often the recorder. So it gets used in every single patch.
Beyond that my usage varies wildly. It’s my super-flexible Eurorack-integrated DSP playground.
Over the years I’ve had it, I’ve learned to not have it do everything it possibly can all the time. Not that there’s anything wrong with that. But of course you will eventually hit the CPU wall with that approach and might start feeling guilty about neglecting your other modules.
I do think it’s a great way to learn it. I definitely focused intently on it for a long time and still periodically engage in deep 301 study. And I think doing that has helped inform in what contexts I want to use it vs another module for whatever task.
That’s probably more vague than you were looking for. But it really varies a lot. One day it might be that the 301 is the only module I have that can grain stretch a sample’s length independently of pitch and stitch it back together seamlessly. Another day it might be that I think the character of the 301’s LPF is really the one I need to bring a particular sound to life.