Sin6 is a beginner/intermediate workout.
Better, IMO, is Slim Series.
If you want to "test the waters" you can get "Keep it Up," a single workout that is a follow-up to Sin6 and a prelude to SS, and also includes a good stretch workout and a good ab workout.
Here is a recent thread about Slim Series that has lots of info:
http://69.0.137.118/dc/dcboard.php?
az=show_topic&forum=4&topic_id=216631&mesg_id=216631&listing_type=search
Some people find SS very boring, while for others (like me) who sometimes like workouts you don't have to think too much about, the repetitive nature of the workouts is overshadowed by their effectiveness (at least when done as part of other routines---I don't think I'd want to do a long SS rotation!).
I find they are good to get me going when I'm not in the mood for anything else. I also like to put on my own music (there is a "no music option," and the moves are very simple, so you can just follow the beat of the music and not the pace of the exercisers).