As far as I know documents have been largely been hidden away. I'll try to explain the current consensus though. (I'm just assuming you're asking after you've just seen Silmido??) If you are asking because of the movie, first know the movie has take a lot of artistic freedom.

Firstly you have to understand the severity of the training. They were subject to intense intense training focused on things like parachuting and survival training including using and carving SKULLS to use as cups and bowls.

Secondly, unlike the movie, NONE of the soldiers in the unit were on death row. Many had committed petty crimes, and some didn't even know why they were being taken to Silmido. They didn't really sign up for the intense training and the mission to infiltrate NK.

Thirdly, the disciplining of the group was extremely severe. Harsh beatings for minor slights were common and deaths did occur.

The revolt didn't really occur because the Government wanted the Unit dead. Evidence seems to suggest that there was no such order and if it did happen the unit had no way of intercepting that order. Current evidence seems to point to the fact that without a clear mission remaining since the SK government no longer considered assassination a viable option due to warming relations, the disgruntled unit under the urging of their lieutenants revolted when there were the least amount of soldiers

Because it's mostly classified, I can't find too many "official" sources, so I'm sourcing most of my information from an eye witness account from one of the few surviving guards from Silmido itself.

http://weekly.donga.com/docs/magazine/weekly/2004/01/15/200401150500020/200401150500020_4.html