Overall I am happy with the Mavericks upgrade. However, I am *very* saddened to see that in Mavericks, the "iChat Theater" feature has been removed from Messages. I used iChat Theater frequently, for years. And I never had a single issue with it. It was a unique feature I haven't been able to replicate with any other software. And the look on the other videconferencing partner's face when they saw it in action for the first time was always priceless. Especially if they were new to Mac. It was one of those differentiating features that made things easy and fun, and practically felt like magic. It was a great way to watch a video together online, or to to present a document/image to another person while you're videoconferencing. So why was it removed? I hope it comes back.