This was a good episode that dealt with Dr. Curt Connors' experimentation process coming to fruition when he fused his DNA with Reptilian DNA thus causing his arm to regenerate. The side-effect was his brain was effected and the Lizard traits started to take control of him.
The most substanative facet of the episode was Peter supposedly leaving Mrs. Connors, Eddie Brock and Gwen Stacy because of Aunt May's curfew when in fact, he went to battle the Lizard to get him under control and transform him back to a human in addition to taking photos for the bugle to assist with the bills. It was a pretty deep episode dealing with his responsibilities as Spider-Man, his loyalty to his friends and his responsibility to help out Aunt May. The episode ripped Peter into 3 directions with him ultimately choosing to help Dr. Connors AND Aunt May with the bills.
Overall, aside from the action, there was an underlying darkness about this episode that forced Peter to make decisions that would effect his relationship with the people he cares about. Additionally, it illustrated that Spider-Man is a tragic character that doesn't always have a happy ending.