You want to read this: http://xdaforums.com/showthread.php?t=1619630
Sounds like you've been very lucky! Most of the ROM threads are full of problems people have had, and custom roms are often only tested so far. The users do a lot of the testing and bug reporting in general use - complete with bricking, etc. That's one of the reasons flashing a ROM voids your warranty!
In my case I've survived flashing an ICS ROM too, but not without difficulties and the route back to GB was even more perilous.
Hopefully you continue to be lucky and aren't posting about a brick anytime soon.
Getting a hard brick is the easiest for getting a warranty claim as Samsung (any brands actually) has no way of telling what happened. Just act stupid saying upgraded via kies caused that, or plainly act dumb even if you are a geek.
Don't ask how I know cause I like visiting support centre for warranty claim. Changed screen, buttons (equal change screen), battery and etc.
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