I knew the whole story going in when I eventually watched the whole show and it merely makes it "good" rather than "great".
Madoka's main enjoyment comes from the plot twists -although the mishmash of art styles is interesting and there are some isolated moments where the show looks particularly good (towards the end, mainly), it's not a particularly interesting show visually and the characters outside Homura and Sayaka are quite flatly drawn (and Sayaka is an idiot, frankly). It is still a very entertaining story, though - just without any of the "OMG WHAT IS GOING ON PLOT TWIST HOW COULD YOU BE SO CRUEL" stuff that helped fuel the show's rabid popularity as it aired.