I never used Notational Velocity, but this seems like an awesome UI to use for Notes. As long as you have powerful search you can always find your notes by their content and create new ones when the ones you find aren't relevant.
How many times I've created a new note related to something I wrote about before, but didn't want to search for. Now I'd basically be forced to search for it when I tried to create the new note and I'd assume this would help keep all those thoughts and ideas at least somewhat related to each other.