I am scared of it, I broke my blog (or at least I am blaming it on that), and I have started getting lots of random hits based of the nav bar. I think that those will recede with time. One thing the nav bar does to well is that it links the blogspot community of people together and makes it an adventure to go find a new blog. All you have to do is click.
Though I like the ability to search my site using google, I would prefer the search that I have access to when I a logged in, but oh well.