Attending a MS congress was always a big thing for me as a developer. Learning something new is exciting and usually it is helping to improve things in my sourrounding a bit with the new knowledge. Strange is that the topics I've followed on such a conference were nearly non existing in my professional work as a dev - but somehow become very important shortly after the conference was done.
Getting inspired for new things is the most important reason for me to attend. Meeting others, speaking with guys directly from MS is another big issue
The biggest thing for me is currently Windows Phone 7. I am really excited about that as I was not about any technology for a long time. Preparing some apps for launch right now. Unfortunaltely the devices in Germany are really really sparse.
As it seems my company will not pay for this time attendance - I was already on one conference this year (not from Microsoft) so the money was (ill) spent.
Hope I could get there somehow nevertheless - maybe MS could ´help here As I live in Berlin, it would be a real miss if I would skip this year...