Pros
Great opportunities to gain experience where you may not have had any, or the credentials on your resume to get you the opportunity in the first place. Lots of room for growth within the company if you work at it. This isn't a place where you can come to work, do the minimum, and expect to get ahead. If you work hard you will. Pretty simple. Lots of support from senior admins and managers available.
Cons
It's not going to be an easy ride. The first year is going to be tough for some people. Be prepared for some bumps along the way, especially if you are inexperienced. There are plenty of people to ask for help, but it can still be very stressful until you get the hang of things. Keep at it and get through this period, and you'll be fine.