I just noticed from Matt Mason's comment on the plug-in migration steps that he is running a very interesting series of posts on the new Revit 2011 API as well.
Here is his current table of contents:
Some of the topics have already been posted, others not yet. We have covered some of the areas here as well, but several not, such as the new ribbon capabilities and selection methods.
Great stuff, Matt, and thank you very much for pointing it out!