Leslie, why do I get the feeling that I'm a the glass is half full type of person, and you're a the glass is half empty kind of person? 
In general, I think I am a glass half full person, but when it comes to movies and books, that's the wrong yardstick to use.
Books: if a book doesn't pull me in quickly, I very rarely plow through it. People who say to me, "Oh keep going, it will catch you by page 160..." sorry that doesn't work for me. I need to be caught by page 10. This is probably part of the reason I never took a literature course in college. I knew there would a problem with must read/can't plow through.
If I like a book, I am likely to read and re-read it over and over. My "pendulum" swings all the way the other way.
Movies (in the theater): I think long and hard about going to see a movie in a theater. I read reviews and want to make sure it is a movie I want to see. If, in that case, I don't care for it, I am sorely disappointed. Probably my best/worst example of this is "The Family Stone." That movie got good reviews (from some reviewers) and I loathed it. In fact, it is one of my all time WORST movies. Even so, in the movie theater, I very rarely walk out. I stick it out til the end....painful. LOL
Most of the time, though, I do a good job about picking movies to see in the theater, probably because of my advance research.
Movies...on DVD/HBO/TV: I can be a little more reckless here. I'll watch something I heard about but that didn't meet my "gold standard" for the theater. In this case, it is more like a book: if it doesn't catch me quick, I turn it off. On the other hand, there are many movies I enjoy and watch all the way through. If I really really like something, I'll watch it endlessly, just like I'll read a book repeatedly.
This all applies to fairly new movies. Historical films or films that are new to me, I am willing to give a try, and am often wildly surprised. That is how I discovered "Wages of Fear" (1953) a few months ago.
This is probably way too much information and way too analytical for you, isn't it? Oh well, it gives you an idea of how my mind works and why it is hard to reduce me to a half full/empty glass. LOL
L