my biochem II class was also metabolism, but i wasn't straight memorization. We got to have some charts on the exams, and the course was fantastic. I don't think it helped for the mcats, but my room mate is in DO school and it DEFINITELY is helping him in his first year. so, i'd take it, but its not a necessity
it wasn't that useful or helpful for the mcat. you can take the test without it. but it is kind of interesting. there is a considerable amount of information to memorize though.