They also did something that wasn't really announced: you can now drill down into every single event a user has ever triggered and look at all the properties. It always baffled me that this wasn't possible in the stream view or when segmenting down to individual events. I use mixpanel not only for reporting but also as a first aid resource when something breaks for a user. It's great to be able to see what they did when exactly and under what circumstances.
I think it's brilliant that Mixpanel lets you measure the impact of email campaigns without having to track opens and send them to mixpanel as events. If there was a way to send emails in response to certain events (such as purchased item X) and then to refer back to those events from within the email, I'd remove all lifecycle emails from my code and just use Mixpanel for that. Can we get that, Suhail? Please? :)