Ok, so I thought I could share this method because it's really easy and quite cheap as well.
I've seen many people on the forum not being able to unlock the bootloader, I gave them advice but it looks like there's too many of them.
The thing is...you cannot really unlock the bootloader when you have: "Bootloader unlock allowed: no"
( you can check by typing in dialer *#*#7372489#*#* then >service info> configuration.) (you won't be able to see it on JJ's ROM, he removed this feature)
This basically means that your carrier prevents your phone to get into fastboot mode. It's the carrier, so don't blame Sony! The reason is obvious, with this configuration, you cannot use different carrier SIM cards.
So if you want to use another SIM or unlock the boootloader to be able to flash all the custom ROMs, you can either do it a pretty expensive way, or do it My Way which I'm gonna explain.
And if you don't give a **** about custom ROMs and just want to use different SIMs, I got good news! It shouldn't void your warranty! - the bootloader will remain locked and but now you will be able to unlock it yourself for free. EDIT: Apparently it unlocks the bootloader too. I haven't noticed this though, in the S1tool test, it showed me my BL is still locked, but one of the users (Patrol619) stated that it automatically unlocked his bootloader. You can watch this video for some useful info. http://www.youtube.com/watch?v=sn-Vubgka1M&noredirect=1
Remember, if you have this configuration, you MUST PAY TO UNLOCK THE BL. So don't waste time looking for a free method.
Go through the steps, you can use a metal wire or a pin instead of the test-pointers if you don't have them.
After you finish, you will be free to use ANY SIM and Unlock the bootloader without losing DRM keys or through SONY.
I think I could mention just one more thing...If you want to unlock your BL without losing DRM keys (there's a guide on the forums) and you get an error, it's probably because of your manufacture number, if it's older than 12w10, so you have to do it the official way by Sony.
I hope this will be helpful to you, I've used this method and it worked perfectly.
Obviously.....I'm not responsible for any damage you do to your device, computer or car or anything else
And last but not least: Press the Thanks button!!