No, he's not bad. Even though Snape was a DeathEater he turned from bad to good after Lily's death. Snape tried to protect Harry Potter and worked as a double-agent to Dumbledore.
Red Flower1: I'd say he is neither bad or good. Though he risks his life multiple times and eventually dies for the greater good/Harry Potter he still decieves (which is never right) and takes some joy in inflicting pain on Harry because of what Harry's father did to him. Since Harry is innocent and Snape never gave him a chance to prove himself as anything other than a mirror image of James this is especially wrong. If Snape had not bullied him Harry may have trusted him more leading to Sirius and Snape still being alive. That being said I believe him to be just human, neither completley bad nor completley good.