Vantaggi
Cutting edge technology (CMOS H/W), very talented engineers, great and grand projects. There are some really smart people here; in the development teams, and in research. It's great to have a research team to help tackle really difficult problems. Also, generous vacation (though you can't always take it and you can't accumulate it), flexible work-at-home deals depending on your area. Decent initial salary.
Svantaggi
Compensation is poor. Once you're in, raises are non-existent or really small. Same for bonuses. And that's for exemplary performers. Promotions are very rare, particularly for the technical team. Management is odd: 1st/2nd line managers spend most of their time trying to be "Project Managers", not too much focus actual management. There's a project management hierarchy that overlaps with these first lines, and adds little value ( though that might be the best career path). Zero training. Zero travel. Development projects are overbooked. IBM is really pushing off-shoring to India. You have to do your job, plus train a team of Indian developers; Middle management is pretty bad, they aim to please Sr management, customers, without consideration to their team. Sr Management reaps millions, off-shores, and lays technical people off ; their is not a good connection between the team and Sr Management. 7-10 levels of managers in between, too much.