One of the current flaw of pp system is that it favors more on score and mod combination, rather than having separate statistics that determines what they're good at.
Some (read: "most") players favor speed on their plays, e.g: DT over HD+HR, HD+DT over HR+FL, and DT+FL over HD+HR+FL, which can be true at least on some cases. It's like an awkward way on getting easy #1 with HD+HR+FL to win over DT+FL and HD+DT plays.
I'm not even good at streams (160 BPM is my current limit), but my pp rank somehow is placed around players who probably could stream 200 BPM, all thanks to my Flashlight plays. This is why I just wished that my pp rank is worse than current, but I hate to not playing challenging maps.
Another thing is Accuracy. Some people hate certain mod combination with perfect accuracy to lose over someone with bad accuracy just because the person has additional HR mod. (Sorry, Saint and Shilkey/Hanyuu-chan, but I know someone who added you into their hate list. I actually don't care about it. ;< )
Additionally, some old maps still tends to be a "pp gold mine". I believe this might be because of lacking dedication from pro players towards those maps.
In conclusion, I don't really like how current pp system works (well... not hating it completely though). I simply played this game for fun and pretending that pp system never exists. Maybe pp system might improve someday (which I'm hoping for), but who knows?
That's my 2 cents.