The short answer is that being stoned slows down your perception of time.
The long answer is that it makes you pay attention to things that you normally would not notice. It’s most obvious when you listen to music. It’s almost like the audio equivalent of putting on a pair of eyeglasses—you just hear so much more of the richness and complexity of musical patterns when you’re high.
It also makes a lot of stuff seem funnier. I think this is because a lot of humor is “in the moment,” and since pot affects your sense of time, making stuff more immediate has the added affect of making it funnier.
In general, I find that I have an easier time “holding interest” in movies, TV shows, and music when I’m high. However, the opposite is true for video games and tasks that require concentration and action. So it enhances your passive experiences, but it can be frustrating and distracting for tasks.
One exception is a certain kind of writing that isn’t really writing so much as idea-generation. I find that I have an easier time thinking of ideas when I’m high. The quality of the ideas doesn’t improve, just the quantity. But later, when I’m more critical, I have more to work with when narrowing down good ideas.
If you ever do want to try it (and manage to successfully get high, it takes most people 2 or 3 tries), I would really recommend watching the movie O Brother Where Art Thou.