I think a barrier to using Notenik is possibly the need for it to deal with metadata in each note. An option to have a collection of simple notes without any metadata considerations might be a nicer starting point for people (and possibly useful for any level of user for certain collections). I know there is a Basic notes collection template but it still takes 3 steps to set up and presents a complex Collection Settings window at the end of it.
On the subject of metadata, I would like to see the app incorporate an inspector panel to the right of the screen to hold all of the metadata (with the obvious exception of body). This could be toggled into/out of view by the user. The main panel would therefore simply be the body text in either Edit or Preview views. I think that would give a much cleaner view and be more inline with other apps - perhaps making it an easier transition for new users.