To what they claim, they took so long because they wanted to implement it perfectly, without battery draining and other issues.
As for the keynote link, you can check engadget.com for all what was included. If you want to watch it, it will be up on Apple.com soon.
And I am definitely going to get the next iPhone with all those features.
Edit:
http://gizmodo.com/5512782/ Check out this video on Gizmodo to see how multitasking works. It's beautiful.