Pros
Working with the leading-industry technology - although some may consider that an illusion. Original company founders are superb presenters. Job security.
Cons
Difficulty to adopt industry-standard practices. Lot of legacy, outdated engineering practices. Engineers get boxed into their area of expertise, difficult to grow out. Very easy to let your professional career stagnate after few years. The company does not lay off under-performers, which may be good for job security, but may have slackers lying around. Leaders are obsessed about cutting costs. This results in unpopular company benefits, and difficulties in what many would consider fairly straightforward hardware procurement at other companies: not being able to upgrade storage to SSD, only 1 medium-sized monitor provided to each engineer, having to work with 5 years-and-older systems, not enough lab equipment (i.e. oscilloscopes, temperature regulators), etc. Some decisions seem to cost the company more money and headaches, when certain equipment has to get passed around (because there aren't enough), and get lost in the process. The leader has never been big on work-life balance, and abuses the "work hard, play hard" spirit. I have heard several jokes here about the engineers being lured with a carrot, to be beaten up with a stick.
