I agree with CKurt! I have been in the past 3 PDC (2005, 2008, 2009) and every conference is worthy to attend in person. No just for the sessions but the chance to interact with MS people directly and other developers from different industries.
For PDC10, I do wonder why MS only have it for only 2 days... What kind of content and announcement can be pack within these 2 days will be interesting to see. Windows Phone 7development? Something to do with slate device development? or even Windows
8 announcement perhaps?
My guess would be that the WP7 O/S is being upscaled and enhanced to maximise advantage on Slate devices. This could mean new hardware and Silverlight.Next / XNA.Next.
Gosh, I envisage many days and months of speculation ahead ...