So there isn't another 100 threads saying OMG I UPDATED AND IM BRICKED WHAT NOW? Okay heres the skinny.
-If you update to 1.1.3 and try to downgrade, incorrect SIM will appear on every firmware, but no bad IMEI.
-If you are just jailbroken, updating is fine, restore first for the paranoid.
-SIM Proxy's (TurboSIM, StealthSIM, NextSIM, ect) are broken, yes that does mean YOUR SIM.
-If you unlocked, you will be bricked, let me repeat.
IF YOU ARE UNLOCKED DON'T UPDATE TO 1.1.3! -
pf update: updating to 1.1.3 using the jailbreak method on Installer does NOT break the unlock - yes, if you are unlocked and jailbroken on 1.1.2, and you use the jailbreak 1.1.3 method in installer, you WILL have a 1.1.3 jailbroken and unlocked iPhone.
-If you are OTB 1.1.2 don't update to 1.1.3, or you can start praying for 1.1.4.
-Jailbreak is broken.
-New baseband, no unlock for 1.1.3.
-Oh iTunes 7.6 works fine, nothing different except the obvious inclusion of movie rentals and what not.
1.1.3 DOES have a new bootloader
DO NOT BUY OTB 1.1.3 IPHONES!
So update if you meet this criteria.
-Your iPhone is unmodded(What are you even doing on a iPhone modding site?)
-You are just jailbroken.
If you are unlocked or like 3rd party apps, don't update.
Downgrading is Possible to use as a iPod Touch, guide is
here.