from what ive seen people on here saying most everyone's had trouble with the QSI one (ive never even heard of them o_O). i dont remember seeing anyone with a 680 having the TSST (Toshiba-Samsung Storage Technologies is what that stands for btw) one, but ive got a TSST drive in my 7422 and its pretty nice
My 8510GZ has a TSST drive...same chassis as the 680 basically. I think it's just dumb luck as to which drive you get...based on supply. My TSST seems fine...but no experience with the QSI to compare it to.
Some of the people who complained though...swapped the machine out for another with a QSI and no longer had the problem. Maybe just a bad run of drives?