My experience was that the Org-mode in Emacs was great. Especially how you could capture notes with backlinks from any Emacs context, and the Agenda view it generates. I went all-in on the ecosystem and wrote my mail in mu4e, for instance, which can integrate with Org-mode for writing HTML mail. Being able to add inline LaTeX equations and syntax-highlighted code snippets to such emails was gold. Having easily executable script snippets embedded in sysadmin notes was useful as well.

As for other implementations of it — including vim-orgmode and every mobile app I tried — too many features were lacking or broken for it to be useful to me. In the end, I ended up going back to MarkDown when I left Emacs. The transition was quite painful; Pandoc helped a lot, but many things in my notes just broke during conversion, so I ended up just trashing most of my notes and spending an evening manually fixing the important ones.

While Org is free and open source software, and it’s often repeated that “it’s just plain text”... I’d like to caution others that if you really use the features it has to offer, you’ll be locked into it just like with most proprietary formats. If you’re not completely sure you’ll use Emacs for the rest of your days, MarkDown is a safer option for a knowledge base you wish to keep over time.