I was just reading the reviews and noticed this comment. Might be worth checking to see exactly which machine is for sale before purchasing it.
...Lastly, I want to mention that you should be receiving the updated model. Initially, when this machine came out a couple of years ago, there were some issues with the bobbin jamming. So I think that is why some people were hesitant on purchasing this model since a number of early reviews mention this problem. But Singer corrected this issue at the end of 2010 or beginning of 2011 and added a blue swirl graphic to the front of the machine. So if you have the machine with the graphic, you're getting the newer version and won't have this issue.