This is the kind of stat I love knowing at all times. I kind of wish it would display the tab count for the current window and the combined tab count for all of the open windows; currently, it shows the tab count of just the current window.
Last week Twitter follower @pa930 pointed me to an extension called Open Tabs Counter, that he claimed did what I asked for above. He was right. It's great. It could stand to be a bit prettier, but hey, it gets the job done.