I'll be honest with you, I normally find event keynotes extremely dull. Some senior guy comes up on stage and rambles on with some spiel that panders to the company-in-question's current or upcoming product offerings that often have little to do with the theme or content coming over the subsequent days - they're just taking a chance to do a marketing pitch to a captive audience. My boredom threshold is low and sometimes I pack up and go out looking for coffee.
Not so with MIX. All I can say is that I was excited, stimulated, amused and overall WOWED by the sheer number and the quality of new offerings that are coming from the company for developers, designers, agencies, custom development shops etc. The demos of real applications that have been built by early adopters were simply amazing.
You can watch the keynote streamed from the MIX site here: http://www.visitmix.com/blogs/Joshua/Day-1-Keynote/
Cool things to watch out for:
Some of the key announcements: