There are tons of sessions, but a few interesting sessions, based on my current interests, that I noticed are:
Session on Surface: Surface has been around for a while, but given the niche hardware and horizontal only design, it wasn't as popular as it had the potential to be. With the Surface 2 there is now support for vertical orientation, it runs on Windows 7 and has a new PixelSense technology for its touch support. My expectation is that with version 2, we should see better penetration.
Session on Mono: I do not recall seeing Mono being talked about much in public forums like this earlier. Given the late entry of Microsoft in the smartphone war, this is probably a way to get some leeway by having deployments possibly on competitor devices. Also read more on this tool from Novell here.
Session on Kinect: Kinect the new XBOX based gaming platform from Microsoft that has awed everyone. With its touchless console and fantastic gesture recognition system, it has become an instant hit. There is also an expectation that the SDK maybe made available during MIX. Watch out for this session also.