Pros
HMJF lends personnel support to very relevant projects, including vaccine development and other, which is very gratifying to work with. The company only exists because the government cannot/does not want to hire more federal employees neither the military has high level scientists dedicated to the projects they are suppose to carry out. Since you can be let go very easily, contractors are convenient. Overall, the benefits are in line with the market. Depending on where/who you work with, you will have good learning opportunities and maybe market exposure.
Cons
The quality and conditions of your employment with HMJF is highly dependent on who you directly work with, since HR does not take care of maintaining an unbiased environment. Annual reviews are forgotten, employees' feedback are not valued, neither the fairness of supervisor's assessment is questioned. As others pointed out, HR is there to take care of the company, not in the best interest of the employees. For the most part, they are incompetent or simply do not care. Do not expect HR to intervene on your behalf for promotions, salary raise or any other opportunity.