My 3G is currently unlocked using Pwnage, a modified 3.1 ipsw and Ultrasn0w. With O2 now offering an official unlock is there any advantage to retaining the custom ipsw or should I just do a fresh restore to 3.1.2 using iTunes, run BlackRa1n to jailbreak, and then, when O2 tell me to, run the O2 unlock via iTunes?