Notae is a minor stroke of brilliance. It is not a notebook app that tries to be all things to all people, nor is it an outliner or glorified to do list. The easiest way to think of it is TextEdit on steroids (doctor prescribed) without any of the harmful side effects that steroids often have. It's not bloated, doesn't have mood disorders (its totally stable) or have an interface that gets in the way of doing things. Because it is based on CoreData, searches are instantaneous across all of your notes. Tags let you add as many category markers to a note as you want, and then sort on these with the tag palette. Being able to lock a note stops you from accidentally deleting or changing things. One of my favorite features is auto naming of notes (your first line becomes the note name).

For a 1.0 product it is remarkably mature and nearly all of its features work exactly as you would expect them to. The exception to this is using the search bar to search for a tag, but since you can do the same thing with the tag palette that is not a big deal. The developer is responsive, and gets bug fixes out fairly rapidly, he is also aware of features that need to be implemented like viewing only the columns you want like the Finder, Mail and iTunes allow. At $15 Notae is worth every penny.