Pros
If you can start as an executive (VP in IBM speak) you can do no wrong. Mistakes are rewarded, and successes are greatly rewarded. If you are not a VP you will work with some of the smartest, nicest (for the moment) and least appreciated people you can imagine. But that is changing. The IBM US corporate culture used to be a culture of cooperation and working together for the benefit of all, and some of the old-timers still have that attitude lingering around. Try to work with them if you can find them, but their numbers are dwindling because . . .
Cons
The current IBM US culture is a culture of open competition beneath a veneer of civility. The 'nice guys' get laid off, leaving the schemers and back-stabbers and team leaders who understand that whomever reports the status of a project controls who stays and who goes. Lies are commonplace as no one ever tells bad news. Low level management is swamped, impotent, and powerless. Yearly appraisals are a farce - the ten percent 'fast-trackers' are openly praised and rewarded and everyone else is left alone or fired. There is no 'meritocracy' at IBM. A true meritocracy would know that it is possible for everyone to be meritorious, especially if you have hired the best people there are. At IBM the appraisal system is more of a lottery where one out of ten is treated as a champion and everyone else, the other 90 percent, are considered not good enough. The 90 percent, the serfs, are expected to fight amongst themselves and compete for the prized top spots. Since the contest for top dog is rigged and secret with no clear metrics, the serfs pretty much ignore the ratings and do what they can. Why work hard when you aren't rewarded? Why work hard when It is easier to play games and surf the web and grab open source stuff and pass problems around. If your job is a game of musical chairs for a year and a mad scramble at the end to pick the loser then why bust your butt? If the stock slumps no matter what you do then why bust your butt? If the company doesn't care about you then why care about the company? Layoffs are kept as secret as possible and happen quarterly. Actually the IBM management style is mostly secretive. Metrics change. What was good last year is bad this year. You never know where you stand. You may get a bonus 'variable pay' or get laid off. Management, even first line managers, are always 'somewhere else' talking about 'something else' and are hidden as much as possible. As a result fear is commonplace. It is every man for himself and nobody really knows what 'doing a good job' means anymore. Some of the best and brightest are layed off so what exactly does 'doing a great job' mean?
