In my opinion an iPhone is incomplete until it is jailbroken. You may not think so if you have never jailbroken your iPhone,before but, for anyone who has and had to go without, you know what I am talking about. The iPhone 4.o firmware update is out and it is packed with all sorts of new features that are very tempting and may make you want to update. But beware, because once you do there's no going back and you won't be able to jailbreak for a while. If you already accidentally updated your phone don't give up hope because numerous exploits found have already been found, and a new jailbreak is on the way.
The 4.0 jailbreak is going to take more work than ever because the updated broke a lot of the apps in cydia including mobile terminal, 5 icon dock, and more. All of these need to be ported to the newer firmware which means there is almost an endless supply of work to be done. There is no estimated time out of when the jailbreak will be out, but with the help of a former Apple employee headway is being made.