I tried it.
The import system is weak. It collapses all notes attached to a record into one file. There is only a single note field attached to any bib record. All the tags are imported from the bib record and all the note tags of individual notes disappear. If you are organized in note taking this is bad. You can only make notes in a side panel, so if you like to write in the big window in zotero, your are SOL.
Your main issue here seems to be note-taking features, so I thought I'd mention some changes in the latest release. You can now add sticky notes and annotations directly to a PDF and those annotations get backed up to Mendeley Web, so you can access your PDFs and notes from any computer. For your style of notetaking, though, I can see why you'd be frustrated. Would you consider adding a
feature request? Of course, you can always use both systems.
It's true that Mendeley doesn't work with some existing university systems. They're working on that.