For me, the most enjoyable is dealing with different people. When walking the halls folks tend to grab you for small problems that sometimes take a minute to fix. There are many other likes for instance; participating in meeting brainstorming sessions, meeting with verticle teams in that IT is always involved in some production related issue. Sometimes that turns out to be the most challenging. The most I dislike about my job (when I was working that is!!!) is that you need to tell the user there data is gone because they didn't back it up or something of that nature. There's always learning going on and one can never learn it all. With new technologies coming about, it is impossible to know it all at once. Specifically if the budget doesn not allow the purchase of said testing equipment to play with.
Having been out of work, I miss this very much and I'm taking a few cert classes to keep up with the times. Hopefully I'll be a little more marketable when the time comes to join another organization.