The PDC 2005 was the best conference I ever attended. Seeing WF and WCF for the first time, as well as the DSL Tools and lots of other stuff, plus the several contacts I did while there, helped understand what was to come in technology, and this help |create|it| prepare for this future.
I am also attending this year's PDC2008, where a lot is expected, for example, in what regards Microsoft's approach to Cloud Computing. BizTalk Services is sure to be there, as well as BizTalk "Oslo", Live Mesh and other initiatives like SQL Data Services. Just check the session list, full of vague descriptions so as to not spoil the surprise, and you'll realize this has the right ingredients to be a great conference again.
I know of several other (Portuguese) people who are attending, and if you can, try to be there. The PDC2008 is about future technologies, and it's the Microsoft conference to attend this year.