"I knew how the movie was going to end".
I've never really understood that comment. As a fan of movies, I love seeing movies I like more than once. It's not the destination that's most important, but the ride there. Any fans of Indiana Jones knows Indy will win, will live, but how he beats the bad guys, the laughs along the way, etc. is what counts.
With "Up in the Air", like many movies I can spot how some of it will end up (I spotted Clooney's girlfriend's arc a mile away) but I put away that urge and try and concentrate on the experience such as the witty dialog, the acting, the chemistry, the reality of the story, all that put together with some originality (did you know a lot of the performers were real people who did get let go in that same situation?) really make my own enjoyment of MOST movies a lot better.
We're all different, but that's my take on predictability in movies anyway.