Pros
It's great to be surrounded by some of the best and brightest people in the world, and research is almost never boring. My adviser as well as majority of the faculty and staff are very competent people. Additionally, I enjoy the company of my labmates for the most part, and when time permits, the State College social scene (be it restaurants, bars/clubs, or other entertainment) is decent.
Cons
Research can easily take over your life. As a result, it's a struggle to find a good work/life balance. Sometimes equipment breaks, things get misplaced or misused, or the lab might be dirty from the person before you. Additionally, a lot of the actual work culture (as a grad student) is dictated almost entirely by your adviser and/or labmates... This can be good or bad, but it's something to consider.