I am very happy that I switched to MUS for my 6th grade ds, and plan to use it for my younger ones next year. (NOt the Epsilon level, but MUS.) ;)
You can send for a free demo CD, which may be of help. Also, the MUS website has sample lessons, FAQs, etc.
I think MUS is on Cathy Duffy's Top 100 Picks list, too. (Correct me, someone, if I'm mistaken.)
Hope this helps, and please do post specific questions, if you have them.