I disagree completely. I wouldn't trust anything important to OneNote, and it's hard to get things out of it again, too. Your notes are basically locked in. You can sort of print to PDF, but it uses different pagination to the original PDFs you annotate! PDFs are inserted as bitmap images instead of vector format, and text is only sometimes searchable.

OneNote has a really scary number of obvious bugs, with pen input especially. Writing disappears immediately or jumps left and right, the document randomly stops updating the screen, the program gets stuck in a high-CPU loop making huge input lag and needs restarting, selecting writing doesn't select what you draw around but a smaller area inside that, etc. It's incredibly frustrating and difficult compared to the Android pen-based notes app I use, Squid (which has a much narrower focus, but is much better at it).