I's not an all or nothing package, I mean if you have blogs and articles, you will need the traditional URLs, but if you have a single page application, then you need hashbangs, there is no traditional way of achieving this, let's say all your content is rendered and you have a tab view on your page, and you want to make sure that if your page gets reloaded, the user would get the same tab opened, you have no better way of doing this.
It does work in FF4, but it's not widely supported enough to rely on just yet, you're right.
I also find the best thing to do is use a hybrid approach (pushState where available, hashbang as a fallback.) If anyone else is interested in implementing this, there are some good frameworks[1][2] to give functionality similar to pushState via the fragment identifier.
Note that these constantly poll the hash in browsers that don't support the onhashchange event. It's a good idea to turn down the polling frequency to half a second or so, because I've found it can cause performance problems in IE.
