(I know that most people won't trust this due to the fact that many kids like to write reviews for horribly inappropriate things saying "THIs iS GUD 4 AGES 4 ND UP!!!!!!!!!!!", but please hear me out with this review.)
One thing that the people at Common Sense Media have failed to mention is that for the first 6 seasons, this show was on the regular Cartoon Network lineup rather than [adult swim], and it was rated TV-PG (Look on the show's wikipedia page if you thing I'm lying.) The entire review on the main page relates to the last two seasons, which is pretty unfair because only 25% of the show was actually on [adult swim]. If you want a parental review of the first 6 seasons, head over to the IMDB page for the show. It has a much more detailed content advisory page that contains different data for each season as the show goes on. I'd say the first 6 seasons would be fine for ages 10 and up, and the rating the Common Sense Media page has at the moment is accurate for seasons 7 and 8.