Pros
IBM used to be a great place to work. They have big company benefits and name recognition which bolster your resume and IBM is highly regarded in the industry. One of the biggest benefits to working for IBM is the ability to work from a home office, which saves you time and money by removing the commute from your daily routine, although IBM does get that commute time back from you in extra hours worked. Another great advantage to working for IBM is exposure to insiders at Fortune 500 companies that may help you in your job search once you're thoroughly disgusted with IBM.
Cons
IBM no longer has respect for the individual. Employees are treated as commodities. Benefits have eroded and IBM no longer pays market for their skills. Some items that are touted as benefits (such as tuition reimbursement) are not available for the employee population at large. IBM used to have a pretty good bonus program (variable pay) but the percentages have tumbled even as the stock has risen to a 7 year high. IBM touts itself as a company that supports work-life balance, but the truth of the matter is that they've laid off so many people that the folks that are left (that haven't been reclassified as non-exempt workers) are forced to work more hours to get the same job done. Also, IBM lags other companies in their own leveraging of technology. My advice: if you have a comparable offer elsewhere, take it. If you work for IBM in the US and haven't already been offshored, it's just a matter of time. IBM is so process-heavy that it can't get out of it's own way. People in IBM use the "process" to avoid doing the right thing for the customer. Way too much red tape for my taste and the customer always takes a back seat to whatever IBM's pet program is at the time.