With Lucas and Peyton gone, there was a lot less good material for Mark Schwahn to rely on. Their relationship, as well as the relationship between Lucas and Nathan has been the heart of the show since its inception.
The series should then have relied wholeheartedly on its three remaining wonderful characters --> the duo of 'Naley' - Nathan and Haley James Scott, and their good friend, Brooke Davis.
(The return of Haley's musical career was also appreciated, although the character of Miranda was not.)
To a certain extent, it does, and I think the two main storylines of Naley (Nathan's basketball scandal and Haley's depression) mark the season for its two halves; whilst Brooke's rocked relationship with Julian and continued reliance on her mother is also well worth watching.
However, it doesn't feel like Tree Hill excepting the above three. Most of the old characters have been written out. There was no mention that I noticed of the wonderful Deb; Skills, Junk and Fergy took a backseat, I felt; Dan's storyline was very good, I have to allow.
Of the new characters, Alex is the best. She is funny and I did sympathise with her. Clay and Quinn --> perhaps, I was jealous of the fact they had replaced (in many ways) Lucas and Peyton, yet I never warmed to them with the only storyline, that of Clay's dead wife making him let go, the best.
There were dud episodes and there were dud storylines and there were times when I wondered where the brilliance of the earlier seasons (in particular, that of four and five) disappeared to. Yet, this is still "One Tree Hill" and I am thoroughly looking forward to season 8.