Pros
The middle-layer, tactically-oriented leadership is still (mostly) sound. There are many hidden pockets of great work if you can find them. Intelligent, broad-minded coworkers abound who care about serving the public interest and share the values MITRE extols. Decent benefits, though less decent than in recent years.
Cons
The cons are many and various these days, though I suspect they are still fewer than in the for-profit sector. First, senior leadership is in chaos. To the extent that there is such a thing as a guiding strategy, it has been to convert MITRE into for-profit company. The culture has shifted from a more egalitarian mode to one in which people are ranked and rewards are distributed more and more unevenly. The focus is on growth and revenue. Technical skill is valued only to the extent that it can be used to develop further business. Growth promotions above a certain level have been eliminated, and the pay structure has become increasingly pyramidal. The company frequently underbids on technical projects, leading to much crushing stress as technical staff scramble to fulfill unrealistic promises they did not make. Project leads typically do not consult technical staff when decisions are being made, and therefore often fail to push back on unrealistic demands made by sponsors. Work-life balance suffers as a result. While it is still difficult to lay people off at MITRE, I suspect that may be changing as well. There have been a number of quiet layoffs in recent months, in addition to one violent bloodbath a couple of years ago during peak COVID. Internal research and development is being restructured so that the sponsor-facing parts of the company have more control over how the funds are disbursed. This is intended to better align that research with sponsor needs, but will likely lead to ever worsening myopic short-termism. That has been the trend over the last few years already, as pressure has increasingly been brought to bear on projects that formerly would not have had to worry about having a clear sponsor transition plan. Principal investigators receive no support in developing these plans, despite the fact that good research is hard to do and really ought to be the first priority. Talented people have been leaving the company in droves. The senior leadership ranks have swollen considerably under Jason's administration. Benefits have been cut multiple times, and seem intended to punish senior staff. I suspect the current fascination with all things AI will only worsen many of the above-mentioned cons.