For a guy that was probably paid tons of money to reprise Han, Harrison didn't mail it in.
SW was never had Oscar caliber acting, but Ford came off very genuine.
I thought he carried the middle portion of the film and helped tie the chemistry of Rey and Finn together.
I really enjoyed the film, its got issues but it sets a solid foundation for the next two. However if I could change 2 things....
1. Han dies in the second film. I wanted him and Chewie to escape this scrape just like the old days...but there's still the regret of Kylo Ren that he knows how to deal with. Maybe not reveal Ren is his son until the second film as well. Is it a bit too close to empire? Maybe, but I felt it was a bit too rushed with everything else going on. So the first movie is really about him setting up the new characters, and the second would be him helping to build Kylo Ren as a worthy villain, not as incompetent and whiney as in the 1st (which I was fine with BTW).
2. Starkiller base should have been the main plot point for the 3rd film, its just too soon for a new death star right away. The 1st order as a whole needs a lot of work, easily the weakest part of the movie.