I was in 11 when the first season came out and have loved it ever since! the first 2 seasons are written and acted beautifully and the film that came afterwards was also great!
Season 3 is certainly the worst part of the series with the whole recasting and 2 returning characters but is somewhat bearable. However, season 4 that has all the characters from season 3 and briefly brings back 2 other characters from the first 2 seasons, and is written better, and does make up for some of season 3.
Overall LOVE this show, especially seasons 1&2 and the film.