And in most of the cases, IMO, not to forget those awesome co-workers who (have a forget-stuff-in-60-mins syndrome and) would need a lot of help on grammar or vocab, every single day. Blessed life, I'd say!
I'd like to know what type of jobs the responders work. Would be interesting to see a breakdown of answers to "how demanding is programming" by users of different languages/frameworks or by what type of company they work at (startup, big corporation, etc).
If you get full control of the code base from the ground up, you can often make life easier for yourself (it takes work and continual refactoring, though). What's difficult is when you have to work through other peoples' messes.
All the problems in the first answer are people problems. If you work in a software firm that doesn't treat its employees like code monkeys, or better yet, work for yourself, then programming isn't demanding. It's fun, relaxing, and awesome.
Many times when I hear the "programming is very easy" claim it comes from someone who is out of work: "Oh, he say programming hard? Not so! Programming very easy! I do this job for you cheap!"