Here’s a little article I found explaining why Jailbreaking your iPhone may the way to go if you’re an iPhone user.
1. Jailbreaking your iphone is an incredibly easy process using the current Redsn0w hack. Obviously backup your phone in itunes before jailbreaking and this will allow you to restore your device to its previous un-jailbroken state if you are not happy with it.
2. No you don’t lose all your existing apps. However the developer of redsn0w suggests:
a) backing up your iphone
b) doing a restore to factory settings (i.e. brand new state)
c) jailbreaking the device with redsn0w
d) restoring from your backup as necessary (this will restore your previous apps).
I have done it this way and it has been perfect.
3. I would suggest that jailbreaking is the way to go as it gives you that extra level of flexibility. Some elements of the jailbreak (such as Winterboard which gives you themes etc.) can be draining on the battery and can thus be perceived by users as being negative, however it is the USERS CHOICE. The great thing about jailbreaking is you can be selective in what features you want. If you just want the ability to multitask (run background apps) then just download that program and thats it. I recommend trying it out and you have the ability to restore if you’re not happy.
4. The pros include the obvious flexibility and access to apps prohibited by Apple in the app store. It allows you to customise your device and make it stand out from the crowd and provides a great range of really helpful features (think video recording on the 3G, calendar on your lock screen, background apps etc.).
The downsides include potential device instability and a drain on battery life when using some applications. Also, Apple will not honour the manufacturers warranty if they see your device is jailbroken.
5. Redsn0w is used to jailbreak your device, giving you access to Cydia and other third party sources of programs that arent allowed in the app store.
Unlocking the phone is done by Ultrasn0w and can be downloaded from within Cydia. If you are happy on your network and have no need to use a different sim card there is no need to install Ultrasn0w.
6. When you install the 3.1 update for instance Apple actually puts a new image of the software on your phone and thus the jailbreak is wiped. Therefore the devs recommend waiting to update your device until they have come out with an updated jailbreak for the 3.1 software. It is more of an issue with people who rely on Ultrasn0w to use other networks because if you update and it isnt compatible your device will effectively be a very expensive ipod touch.
That being said, the recent 3.01 update had no effect on the baseband (which would render the unlock useless) or on the ability for redsn0w to jailbreak your device. So it really depends on what kind of update apple issues. Sites like this and the official dev site will provide you with information on what software version redsn0w is currently compatible with.