I love P and have used it for personal projects (like OSWALD^1) and at work (for some Redpanda components).
I find it very approachable. If you know some basic theory of distributed systems and have been exposed to actors and state machines before, you should be able to have some non trivial models in a few days at days.
Things get slightly more complicated when you begin to ask yourself whether or not you have validated enough of the state space to have confidence in the design. The verifier has a much of options who care poorly documented.
Recently, P was extended to support exploring the entire state space (PEX mode) as well as a prover. These have only rudimentary documentation. I learned about them more by looking at code.
1: https://nvartolomei.com/oswald/
