Good stability, but not a place to develop your career.
Pros
My first boss at ManTech was very concerned for her people and went out of her way to look out for them. She would push back on corporate if she thought there were things that weren't right, and wasn't a "spotlight grabber." The team I worked with was very good, but also isolated- we were on site with the client and weren't really plugged in with what was happening at ManTech HQ. The benefits package was good. Also, they were willing to be open-minded about my resume--I came from another field and background. I think that my experience was very isolated though- I only worked on the one contract. I was lucky that it was with great people that I still keep in touch with.
Cons
Because we were on the client site, we felt very isolated from ManTech HQ. We felt like we didn't really matter to them, as long as the contract was making money. Also, there was very little room for professional growth. They were good about reimbursing for things like PMP training, but then there wasn't really any place to go. I ended up taking on a colleague's role after he left, with an increase in responsibility, travel, and time in the office. I asked for a raise to compensate me, and was denied. After that, I felt like I had to leave- I couldn't afford the associated costs with the travel for the job.