I'm running 2.0 firmware now on my 1st gen iPhone and there are some nice improvements, especially the App Store.
One free app I recommend checking out is Pandora. You create a custom 'radio' station by entering the name of an artist you like, and Pandora will find similar artists & musical styles and stream those to you automatically. Create several stations with whatever musical styles you like. I am very impressed with it.
Also, Exchange integration for mail, contacts and calendar is working well. This was the big hurdle for many business users, and although the implementation is not perfected it is a solid step in the right direction. I am pleased with Apple's delivery on this so far.