Pros
Work/life balance is the best you can get (but see the flip-side to this coin below). Job security is the best you can get.. The training is good (big $ spent on that) and if you apply yourself you can quickly become an expert in both tax and audit. Interesting work (if you pick a good city, you will get to work with a variety of different industries).
Cons
It's a 40-hour/week job. Period. And you will get paid the same as everyone else at your grade, regardless of individual accomplishment. No opportunity to earn more and promotion within the grade/step system is based on seniority. Performance is graded by ability to follow the IRM, not by results ($), which is frustrating for those who are results-oriented, but admittedly, I can't think of a better alternative. Requires a high-tolerance for mindless paperwork, most of it merely for evaluative purposes (e.g., check sheets to "prove" to the case reviewers that you followed the required steps in the audit).