Pros
Harvard overall is a good employer. It offer fantastic benefits including subsidized education at Harvard, great medical (access to world's best doctors at Harvard Med and other perks. Administrative work can be fascinating. You are a part of a team that helps run one of the world's most prestigious and high impact research universities. Great colleagues, everyone is incredibly smart, kind, and fun to be around. Depending on the group, your work can be interesting, challenging, and very meaningful. There are opportunities to jump across groups, schools, and departments at the University. So you can redefine yourself in many ways. For example I was able to jump from IT to the provost office.
Cons
Career advancement is challenging. There is an attempt to get better at defining career progression maps, but they're often incomplete or not fully thought out. It's hard to get feedback on how to grow within the organization and performance reviews tend to be vague. You're at a non-profit, so salary is often a bit under market. Raises are essentially the equivalent of cost of living adjustments usually in the 2-3% range. Staff are often second class citizens to faculty, students, and researchers. It can be difficult to engage the academic community and often the interaction is discouraged. There is a bit of underhanded classism, though its not malicious or intentional. You're more likely to be heard and respected if you have a phd, or have an IVY (really Harvard) degree attached to your name.