That Microsoft was going to increase support for dynamic languages is no surprise: they've been talking about that since (at least) PDC '03 and various hires and initiatives have clearly been in the works. I haven't seen the DLR yet, but my big question is: what version / runtime / patch level of the CLR and libraries becomes the lowest-common denominator for Silverlight (i.e., cross-platform, in the browser)? Because for better or worse, that becomes the platform for dynamic languages in the .NET world.
I am surprised by the IronRuby announcement (and officially bestow the He-Man Programming Award to John Lam). I really thought we were going to see some form of Ruby#:Ruby::C#:Java. Although I'm happy (Ruby is now my #1 administrative programming language), I was actually hoping to see a new language. Ruby's a fine language, but it doesn't have a good story for concurrence, it has a boring model of XML (unlike VB), it has some unattractive Perl-isms. Most importantly, I think MS does a good job when they have the flexibility to evolve the language and, simultaneously, can devote the resources to developing the compilers, libraries, and toolsets.