Some folk don’t like the UI, but it’s consistent across platforms i.e. Windows, Mac, Linux, which I feel is a valid sacrifice. But really it’s like anything...hover the cursor over something and you get tips
It’s a powerful mathematical toolbox. Lots of functions. Don’t feel you have to use them all
There are lots of “getting started” type tutorials out there on the Internet, Harry’s videos are a good place to start.
I have the utmost respect for other - especially free - tools, but I’ve found PI does a great job worthy of the entry price.
Disclaimer: these are just my opinions please regard them as such