iPhone unlocking...

Here is how it works


If u buy an iPhone from Apple ... if u don't wanna use it with AT&T ... you need to use iNdependance to Activate the Phone, then JailBreak the Phone and then install SSH on it. Once u have that done then u upload AnySIM on ur iPhone and it unlocks your phone so u can use other non AT&T sim Cards

However, u can not update to future apple iPhone updates without bricking the phone, so that is what iPhone Dev team and other teams are for, they post guides how to revirginize your phone so u can set it back to original settings that way u can update to the new firmware when that happens and that way u will be up to date (but foolishly updating will BRICK ur iPhone and u will have an expensive iPod in your hands)


If u buy an iPhone and u want it to be with AT&T but u want 3rd party apps, all u need to do is JailBreak your iPhone and install installer.app and you are on ur way to 3rd party applications, and before u update to a new firmware all u do is restore your iPhone to original settings in iTunes and ur on your way


Usually when apple comes out with new Firmware updates they break the old code that allows you to unlock or install 3rd party applications on your phone so i would wait for others to figure out how to use 3rd party apps as well as unlock new firmware, for now no one knows when new firmware will come out


Hope this helps

 

If you unlock the iPhone and then update it, it will re-lock it and you run the risk of 'bricking it'.

That's how I understand it anyway.

EDIT: Much more comprehensive answer posted while I was composing mine.