I just got the new iPhone 4 (4.2.1) and I decided I would like to jailbreak it, but I am scared of voiding the warranty and causing it to slow down or worse. I do have an iphone 3 which I successfully jailbroke on Sunday using green poison. Since that time, I've been able to change themes on the wallpaper and SMS page. What I am wondering is if I do the same to my iphone 4, will it void the warranty? I am afraid of doing this in case my iphone breaks and I need to send it to Apple for repair. Also, will it cause my brand new phone to slow down? Please let me know. I really want to jailbreak it but I am worried about all of the things above. Thanks!