Pros
Stability and job security, formerly.
Compressed work weeks and work-life balance, formerly.
A 47-year no-layoff policy tested in two recessions and a pandemic. Formerly.
Now? Well, all of those are gone, so it's hard to really cite anything other than that there's health care and the paychecks don't bounce.
Cons
The same stuff that's always been there, for one. Strict dress code. Dated systems they're trying to run away from as fast as humanly possible. Strict in-office culture with limited WFH. Little to no upward mobility; most senior management has been there for 20+ years and when someone does get promoted, the remaining jobs often seem to magically go to their buddies without getting bid. A complete inability to manage and coordinate anything effectively amongst multiple teams, which apparently is going to be somehow solved by laying off almost all the project/program managers.
Oh, and on top of all that? Now, the new regime will lay you off, but first they'll gaslight you and claim the no-layoff policy never existed. Then they'll claim the team managers (who they conveniently also laid off) did the rankings that determined who got cut. Then they'll put a bunch of the survivors into a "bootcamp" and then make them interview to keep their jobs.