Pros
NIH has a great mission and is saving lives. Each Institute, Center and OD Office is different and offer different privileges. They range from flexible work schedules to full-time telework. Since there are so many opportunities to move around to different ICs or OD Offices, you could get your foot in and find the best fit down the line. NIH does seem to value a work-life balance. There is also a very diverse workforce, especially in the labs.
Cons
It's the government, with all the government bureaucracy, closures, changes in priorities due to a change in administration, etc. There also tends to be a tendency to advance people who really shouldn't be in leadership positions, reward people (favorites) just for doing their job and not hold employees accountable for poor performance. However, that's not dissimilar to any corporation, either.