I had a pewter Sin back in 2004/2005 that I used for a little bit of everything, from dirt jumps to even a dh race bike when I was in between full moto mode and trying to decide if I wanted/could stay in dh racing. Honestly, the only thing I ever wanted with the Sin was a slacker head tube angle. For a majority of the local east coast (mid atlantic) races it was the perfect bike, as the smaller courses with tighter corners and lots of pedalling sections really played to what that bike did well. However, on bigger courses that turn the speeds up a few notches, things got a little out of control at times....but it was never meant to be that kind of bike, I was just using it for something beyond it's intended purpose.
I ride/race a 9.5 now and really like the bike, but on smaller mountains I often find myself wanting the Sin because of how I liked to make more out the mountain than the trail gave the rider. By that I mean, I'm always searching for small lips in the rock gardens or even small humps in a trail to launch off of, things to gap over, trying to find unique lines to spice up the trail......not that the 9.5 can't do that, cause you can certainly make it do that, but the Sin had a almost natural ability to be playful and was light enough to do whatever you wanted whenver you wanted to do it.
I beat the crap out of my Sin, I had a 66rc on it and literally rode it hard and put it away wet daily when I worked at Snowshoe Mountain in West Virginia. I beat on it and it just seems to come back for more every time. I've seen pics on the net of them broken, but mine just seemed to be solid....albeit a bit tight in the head angle, but I got used to that.