The best part is...

What do you enjoy most about machinist work? What do you dislike the most? Is it challenging? Are there many opportunities to learn and advance?

What keeps you at your job?

I like the fact that I get to use both my hands and my mind, and I get to see the results of my work. Also, your accomplishments are easy to quantify, so if you excel, it really shows. Good machinists are hard to find, and any company worth its salt really appreciates them. By the same token, a good machinist can go just about anywhere and find a job, at least here where I live.
What I don't like: Very few people really understand What's involed with our work. They seem to think it happens by magic. As a machinist, you can literally watch most people's eyes start to glaze over when you try to explain to them what a particular job is going to require. Good machining takes time and costs money, and that can earn you alot of enemies among the bean-counters at a given company.