this is much better than Jailbreaking. It is a permanent "unlocking" of the phone. We call it "rooting". Its called that, because the process unlocks the Root folder of the operating system and allows you to make changes to it. On xda-developers.com you'll find a Superguide that will walk you through unlocking the bootloader and gaining root access. Eventually one of the developers will probably build a program to acheive all of this...kinda like the Ace Hack Kit for the Inspire 4G, or Superoneclick for numerous other android devices. My only advice is that you ask NOOB questions here, and not on xda-developers.com. They are a great resource, but tend to not be very tolerant of new users. Not big IOS fans either...
So far i'm not seeing any ROM's that I want to flash yet, but give it time...soon there will be tons of ROM's, and you'll have a blast finding which one you like the best!