Talking and flying at the same time was probably the hardest thing for me. As a student, you're used to sitting there in the left seat in your own little world. Now all of a sudden you're in the right seat trying to talk your head off and oh by the way, looking for traffic, keeping track of time, and making sure your student doesn't kill you. A CFI has a very high work load, especially in a high traffic area.
When you're a CFI, you're running the show. You're going to find that time management is going to difficult. You'll go up on a 2 hour flight and before you know it, you're out of time and you didn't get everything done you wanted to. At a Part 141 school with a syllabus, this becomes challenging. What helps is reviewing your stuff the night before and having a plan.
Spin training is no big deal. I got myself all worked up about it too, but afterwards, I thought it was actually fun. I would bring a few sick sacks just in case!
Depends on where you work, but I was paid the same whether I was in the air, on the ground, or in the Frasca (sim).