After a few days of playing with the new iPhone 3GS I have found myself missing the freedom I had with my jailbroken 3G. It's true that I did not have the speed I have now, but I miss the ability to really make the phone mine. Most of the items that I find myself using would have been available in the 3G with an OS 3.0 upgrade and I would have gotten more with a quick jailbreak.
I do not see the current implementation of Voice Control or the magnetic compass as compelling enough to be worthy of an upgrade if you have a jailbroken 3G with OS 3.0. Even if you are new to the iPhone scene you might still be better off with a $99 8GB 3G and redsn0w.
Considering the hype that was evident at the WWDC launch of the iPhone 3GS, I feel let down by this new release and have been having buyers' remorse, something I have never had with a new gadget before.