Pros
IBM has a low bar for hiring engineers, so if you're having trouble finding an SWE job at GAFA you can probably get one at IBM (once the job market opens up again).
Cons
IBM used to be famous for putting its employees first. When I joined, I was told about how good the benefits were, and how IBM was a "family." In the past few years, that philosophy has been discarded. Every few months upper management makes sweeping policy changes, with no employee input, that significantly hurt US employees. When employees react en masse with concern, alarm, and constructive feedback, they ignore or gaslight us, or commit the strawman fallacy by mischaracterizing employees' concerns and then dismissing them. For example, in November 2023 (right after the employee engagement survey concluded), the did away with 401k matching, replacing it with a novel financial vehicle called an "RBA" with much lower yields, and tried to spin it as a good thing for us. Based on publicly available information, I'm estimating that this will probably save IBM at least $100M over the next decade in US benefits payouts. It also means IBM holds our retirement money, rather than the employee. IBM simply does not care about retaining talent right now -- if you are a senior or well-paid employee in the US, they see you as an expense, and they're showing you the door.