From Apple's site, here are the new SDK features and improvements.

In App Purchase

Allow users to purchase content or services from your application using the Store Kit framework. This new framework handles the financial aspects of the transaction, processes payment with the iTunes Store, and provides your application with information about the purchase.

Wired is reporting that the iPhone 2.2 firmward will include podcast (audio and video) download over 3G (previously only available thru syncing, either wired or thru .Mobile) and some updates to App Store. 

http://blog.wired.com/gadgets/2008/11/iphone-22-to-ge.html

 Man, what a great story on the power of a pretty decent SDK and a built-in distro/advertising channel (even with the  Apple commission). This guy wrote Trism by himself and has made $250k in the last two months.  

 Just read this article over at CNET concerning Apple blocking some apps from the iPhone AppStore, for having "duplicate functionality" with respect to built-in iPhone Apps. This is too bad to hear.  The built-in apps aren't revenue generating for Apple, so i'm not sure what the reasoning behind this is. If someone comes up with a better Calendar manager, or better Mail program, why not let consumers choose, just like on the Mac platform. 

[update]

Here is the list of API changes to the iPhone SDK from 2.0 to 2.1.  most of it is in the Audio Toolbox, but no iTunes/Library access additions. 

so i keep seeing articles (http://www.latimes.com/technology/la-fi-apple25-2008aug25,0,2200545.story) discussing iPhone Developers worried they'll get sued for discussing anything about the iPhone SDK and development, "even with friends." uh oh...

i haven't read any accounts of actual Apple lawsuits, or even cease-and-desists/threats. so is this just Apple/iPhone haters posing as iPhone developers, making an anti-Apple stink about nothing, just to get their hate on? or publishers/writers, who aren't ready to actually publish their iPhone Dev books, drumming up publicity?

if you want to develop for the iPhone using an older PPC-based Mac (running 10.5+), there is a way. the guys over at 3x9 and TBradford.org have a good summary of what works. essentially, you should do the following:

1. download and install the latest iPhone SDK

so i originally set up my development environment, keys, certificates/profiles, etc on my laptop. i then wanted to do some work from my desktop (old dual G4. another post coming, describing how to get XCode to work with the iPhone SDK on a PPC).

if you're all signed up as a iPhone developer, and you have all your certificates and profiles set, but you're still getting the following error when trying to debug your app on an iPhone/Touch:

Your mobile device has encountered an unexpected error (0xE8000001) during the install phase: Verifying application

check the following:

• in your Info.plist , make sure the Bundle identifier field is set to your AppID (minus the Apple prefix hash), ie: com.yourcompany.${PRODUCT_NAME:identifier}