I'm about 19 hours in, and I just had the big reveal. I already knew what it was, but it was still cool. The last place I need to go is Korriban, which I left for last since it seemed to make sense.
A bad thing happened to my brother while playing the game. He was having fun, and had been playing for a total of about 20 hours, and he became the victim of the "Carth Glitch". Since he had no other save, he basically has to start over.
for those who don't know, here's a description (contains minor spoilers)
Click here to see the hidden message (It might contain spoilers)
Basically the general idea of this bug is if you enter a cut-scene with a character using stealth, the game will not progress beyond that point. The most common place this is seen is on the Leviathan, if you use Mission Vao to use the computer to open the cells to save Carth, your main character, and Bastila while in stealth...Carth will just sit there nodding stuck on the same line.
It sucks that it happened to him, although I'm glad it didn't happen to me. The weird thing is, he almost never uses Mission, and never uses stealth. so the time he decided to do it, it lead to a game ending glitch.