- Web clipping. Evernotes browser plugins are pretty darn good here.
- Notes with attachments (images, PDFs, etc.). Some of these are mixed-media notes, where text, images, and/or file attachments are mixed to create a comprehensive document about some topic. Others are "pure" attachments, e.g. "store this PDF where I can retrieve it by search".
- Note taking. This, in isolation, is the easiest.
- Note syncing, mobile and desktop. This gets a bit harder.
- Search. Let's be clear, this was the first and biggest killer feature of Evernote. Notebook and tag organization are important, but rather than just providing direct hierarchical/taxonomic organization, they're largely there to support search with user-defined search facets.
I'd also love good Markdown support – that's one of my most-wanted features from Evernote in the first place.
The dropbox text editor works 'ok'. It's not great, but it's clean enough that I can edit my markdown notes and they'll be synced with dropbox.
Requires a rust compile of the code in the plugin, but once that's working it works well.
I think markdown is the most future proof technology for the moment because you can just use pandoc to convert it or most note systems will accept markdown as an input format.
I'm not sure how tags would work in markdown, I guess you can create links manually but that's not really what you want.