Pros
Good benefits, respected company, good people, competitive pay. As a sales person IBM has name recognition with customers, which helps get your foot in the door. Was a better place to work when I started a few years back than it is now.
Kontras
Tough to advance, unclear career paths, not enough focus on career development, hardly ever give raises, constant change in strategy - never stick with one strategy long enough to gauge its success, lots of bureaucracy (too many systems and tools, too much reporting required), not great at rewarding/recognizing success, risk/fear of layoffs. Pay plans are convoluted to the point where no one really understands exactly how they get paid. Every year I worked there they changed the pay plan to pay us less and very few folks got raises (and those who did said the raises were a joke). They have been cutting back recognition programs the last couple of years so high performance isn't really rewarded anymore. Job is always at risk to be eliminated - lots of layoffs in inside sales the last few years.