The firmware 3.1 for iPhone has been released for a while. Every time when I plug in my iPhone to my Macbook, the iTunes reminds me always of a new iPhone OS available. But I must say no to iTunes every time. So why I don't want update my iPhone to that version 3.1? There are 5 reasons or at least my considerations.
1. PwnageTool 3.1 (http://blog.iphone-dev.org/) is ready for the go. AppSync for OS 3.1 in Cydia is appeared too. (Instructions)
2. iPhone OS 3.1 has the funtion that man can arrange the application layout directly in iTunes.
3. Genius Mix will be supported.
1. For non-Standard accessories there are still no hacks appeared like 3.01. The magic is called iapd. It fixs the problem with the message "This Accessory is not made to work with iPhone"
2. It's possible to develope iPhone applications for jailbroken iPhone 3.0 with a patched XCode 3.1.3. (Source) But until now, I didn't get how to make it work with iPhone OS 3.1 and XCode 3.2.