I like to think that I know C# pretty well, but I must admit I haven't had that much time to fool around with .NET 4 as I like. I knew about dynamic types and ExpandoObject, but I didn't know you could operate on the ExpandoObject as a Dictionary, something which (IMO) greatly expands its viable usecases.

If nothing else, at least you enlightened one .NET developer and I'll definitely bookmark your post for future use.