iOS 4 Jailbreak and unlock has been released by the iPhone Dev-Team — but read this before upgrading!
Alright kiddies, you’ve been asking for it, so here it is.  The Dev Team has officially announced their jailbreak and unlock for iOS4.

There’s a few warnings though, you must:

    * Own a Mac (if you’re a 3GS user, there is a windows solution for 3G users)
    * NOT have jailbroken previously with Spirit
    * Have a previously jailbroken device

If you have never jailbroken before and have upgraded to iOS4, you’re out of luck (for now).  If you’re currently still jailbroken on 3.1.2 (haven’t used Spirit on 3.1.3), you’re good to go. Most of the reason is that the exploit Spirit used on 3.1.3 has been patched. This will also leave out 3GS users with newer basebands that came stock on 3.1.3.  If you’re an unlocker, once you are jailbroken on iOS4, you can proceed to using ultrasn0w in order to unlock your baseband.  It will work on ALL versions of basebands, not just old.

Questions about upgrading or whether your device is okay? Check out the Dev Team’s blog before doing anything! And if you’re wary, we’d recommend staying away. I’d assume a PC version will follow.  When that will happen is anyone’s guess.  Have questions or concerns? Leave them below.