As I watched the OSX part of the presentation I kept thinking about the complaints, and wish-lists I hear on forums like this...... and to me it seems they have been listening.
Fullscreen/multi-monitor support is definitely something that comes up often here. Improving Finder (the tagging is just icing on the cake), been hearing that one for years. Want for better battery life, and an update similar to Snow Leopard where focus was almost entirely under the hood. Didnt even know I would want Maps on a desktop/laptop until I saw them demonstrate it and its integration with iCal and iOS.
To me this OSX update is a winner. Every feature, be it under the hood, or something I can interact with, is something I actually want, and will actually use. Well apart from keychain icloud cause Im so deeply invested in 1password - otherwise I'd use that too. Really looking forward to this one, and well done to all the Apple team.