Well if you want the skinny on 2010 to make a pitch for 2010 over 2007 I would sum it up in this line:
"2010 will support improved Social Networking, improved ability for your users to find each other and share information together."
MySites was the weak arm of SharePoint 2007. SharePoint supports teams and departments very well. If does not necessary scale up or down well. It does not support entire Enterprises and their links to other Enterprises and hopefully 2010 better accessibility and performance will produce a tool that can sit at the top of a company and manage its internal and external IM.
But where SharePoint really feel apart was in trying to be a twitter or facebook of the company. It was not just that MySites lacked features, it was also that customizations of mySites were very difficult. Applying customizations to pre-existing sites was far more complex than it should be, and even if you did what you got was not that great. Actually I have rarely seen mySites used as anyting other than a document store.
SharePoint has a large hill to climb on this. Companies must know that other companies own most of the collaboration and knowledge creation of thier employees. Staff are collaborating on Twitter, Facebook, Buzz and using emails serves like Hotmail ratther than creating knowledge in the organization.
Social networking is key to overcoming this and keeping knowledge creation in to the firm where it can become IP.