Pluspunten
There are a number of reasons why IBM can be a great fit for you. Most importantly, the company encourages a healthy work/life balance. Time off is abundant, and the hours are not rigorous. In addition the company treats many employees as "mobile" workers -- working from home or working out of an office as needed. Also, since the company is so large, there are a number of perks and benefits. So, if you are interested in a relaxed work-environment and lots of flexibility, this is a great option. Also, the IBM name on a resume is a great asset.
Minpunten
IBM does have some challenges, and is not an optimal choice for all. Since the "mobile employee" concept is enforced for many groups, it becomes challenging to develop a sense of teamwork or camaraderie. There notion of the office "water cooler" is non-existent. One might argue that such "off the record" interaction does not necessarily contribute to productivity -- the issue is that inter-personal, informal interaction is limited. The other challenge is one that many large companies will face -- different groups are often incentivized in different manners. It is not uncommon to have internal groups encouraged (and rewarded) to operate along divergent paths. Lastly, you will come across an arrogance at IBM -- that "Big Blue" is infallible.