I love that I can dump all my knowledge there and have it be easily searchable on my PC, phone, etc. I love that I can take notes, attach PDFs and images, or make my own canvases and excalidraw diagrams. It's awesome and flexible.
I hate that it's not FOSS. I appreciate that it's an open format (plaintext Markdown files) and prefer closed app and open data to the reverse (Joplin is open source, but mangles notes into a database). I'm strongly considering giving logseq a try, but some of my favorite obsidian features have become a crutch that I don't know if I want to live without.