In my experience, my day always ends up being better when I'm making eye contact. Not only do I not bump into people (because I can tell where they are going), generally you get better responses from people, as they see you as being more approachable/honest/etc. People remember you.
On the flip side, if you have a desire to be invisible, walk around not making eye contact. Hardly anyone will remember who you are.
That's purely anecdotal, but try it for yourself.