Personally I hate being in a packed cinema cos more often than not it's full of kids/idiots that talk through the film or laugh at inappropriate times (I recall going to see Paranormal Activity 2 the other month and they ruined the build of tension with the inane laughter).
I prefer a less busy cinema as I don't have to get up every 10 minutes to let someone go to the toilet. I usually have one of those Icy Drinks. And I like to sit around the middle of the middle row.
But home is a very close second (don't have to deal with the stupid public) especially now I have a Blu-ray player and 32inch 1080p LED TV