So I finally folded and watched this anime yesterday and I'm very glad I did. Madoka,(Also known as "Puella Magi Madoka Magica") is a magical girl anime(Card Captor Sakura, Magical Girl Lyrical Nanoha), but it's not your typical magical girl anime. Where as most are generally light hearted, cute, and somewhat comedic affairs, Madoka is very dark and somewhat depressing. It explores some themes not normally seen in magical girl animes like death, betrayal, and sacrafice. It really surprised me just how much I enjoyed it and just how different from other series in the same genre. If you haven't seen it yet, I highly highly recommend it.
Also, Mami is awesome