Fall is definitely my favorite season.
I find that it's the season in which I make the most personal progress. For some reason the changing leaves, the cooling weather, makes me feel like I'm coming out of a hazy dream. It wakes me up and prompts me to review my life.
I also do my best work (as in, job) in the fall. In the summer it's so pretty out that I hate being inside, and that distracts me. In the fall it's still nice to be outside, but inside becomes the warm comfy place. This takes a psychological load off and increases my focus; I don't feel like I'm wasting time by being inside, so I can sink into my computer-based work and flow more easily.
The concept of “spring cleaning” applies but for me it happens in the fall. I know I'm about to spend a lot of time indoors so I clean out all the unnecessary junk in my place to make it as habitable as I can.
And of course, North Carolina is a state cut out of a forest so the whole place becomes a beautiful mix of green, mute browns, soft oranges and blazing reds for two months. It's really beautiful.