I just watched this video and I quite enjoyed some of the insight that went into the creation of Tumblr and kudo's to David for not doing the cliche thing which is to knock other tools; instead he believes in a "horses for courses" mentality whereby Tumblr is used for certain reasons, whilst other people still prefer WP (or others) for other reasons.
Having myself been through various ups & downs in terms of blogging and content-creation over the last 4 years, I can attest to everything David said in the little interview. Heck, this even saw me move to Tumblr, which was quite a significant thing considering I'm co-founder of one of the biggest WordPress companies on the web.
Since then I have however been able to move back to WordPress (powered by Woo of course) and I now have 90% of the functionality I had with Tumblr, plus the added benefit of not battling Tumbeasts and owning my own data.
Hopefully within the next day or two, WooThemes will be able to release a little something that too will give you Tumblr-like functionality on your own, hosted WordPress-powered platform.