Pros
My review applies to the Beaverton site only (I have less visibility of the other sites), and it applies to engineering only: Formfactor is the only high tech company (mid or large size only) that I aware that doesn't age-discriminate. I have seen may work places, which includes many places in the CA bay area. I know, all companies claim they don't age-discriminate since it's the law. But of course the truth is different. You may not care much about this if you are reading this review after graduation looking for a job, but you will learn to appreciate it when you are in your late 30s/early 40s or older. Formfactor is one of very few mid+ size high tech places that even hires senior people as individual contributors. This is rare in the tech sector, but it may also be a result of the fact that probecard technology (in general) is not as 'cutting-edge' as other high tech technologies (like lithography node shrinking, artificial intelligence, etc). Therefore, skill sets don't become as 'obsolete' as in other high tech companies.
Cons
Management tends to 'pigeon-hole' employees, meaning that employees are sometimes signed up for responsibilities that are below their capabilities, which is detrimental for career development. Another con is management's hesitation to add headcount when the company is doing well (to avoid or reduce layoffs in downturns). While that can also be seen as a 'pro', the downside is that some interesting development projects may get cut during cycles when the company is doing well (in order to move heads to critical under-resourced areas). Cutting back on development is not something that has hurt the company (I believe) due to the long life cycle of a probecard technology (in contrast to more 'cutting edge' technologies in other industries - see above), so this strategy may work but it is your decision if it is good for your career.