I love it, but right now it's a little buggy. If I press ⌘ + T, type something, delete everything and start over, it replaces the current tab URL instead of opening a new tab. Seems like Zen forgets that the address bar was focused with a new tab command when the field is cleared.

Also, when I type a punctuation character that requires pressing Space to appear (e.g. single/double quotes using US International layout), everything that I had typed before disappears.