nvALT is very basic relative to Notes. It is a clone of Notational Velocity witch the killer feature is an original interface focused on incremental search. The same area is used both for creating notes and searching. I.e., in the process of entering the title for a new note, related notes appear below, letting user file information there if they choose. Likewise, if a search reveals nothing, one need simply press return to create a note with the appropriate title.
Zotero is not dedicated to note-taking but to collecting and sharing references. It is however possible to associate notes to them. Zotero is available for Mac, Windows, and Linux.