Matt Cutts of Google posted a video yesterday on the topic of implementing AJAX navigation that works best for Google's crawlers.
The question was, do I use pushState or hashbang (#!) when managing the AJAX navigation on my web site?
The answer was, if you can, use pushState because Google doesn't have to do any additional work to understand it. Matt Cutts explained Google supports both but when it comes to hashbang (#!) Google needs to do extra things to understand it properly.
Here is the video:
Forum discussion at Google+.