In the past few years nothing new has come from Microsoft that has really been a big deal. MVC and Razor were great and a pretty big deal, but everything else didn't really affect my day to day job of developing apps.
Deploying ASP.NET apps has always been a real pain in the neck. Sure, in theory it's as easy as xcopy, but once your apps start growing and your configuration grows it rapidly becomes a bigger thing to maintain. It takes a lot of time, there's lots of stuffing around, it's very fiddly and generally a PITA.
If I understand it all correctly, being able to package up my application into a sort of "mini vm", that has everything pre-configured, would be absolutely bloody amazing. Having it run on this new "Nano Server" thing sounds fantastic - it doesn't have a GUI or 32 bit support, so in my mind it should be much faster, quicker and much easier for remote administration.
I've been waiting for this announcement ever since I wrapped my head around ASP.NET vnext, and now that I think I get it, the future is looking cool. Good job MS.