Pros
The best reasons to work for IBM are one, name recognition, second, the opportunity to work anywhere in the world and finally very good advancement opportunities. I met a lot of great people.
Cons
I found IBM slow moving....also there was this "one size that fits all mentality" that really hurt productivity. The biggest disappointment for me was I thought IBM was a place for growth, training and long term employment. It really turned out to be a typical US company these days...ie no direction, no training and the minute the stock falls there's an employee fire sale...many employees I meet said management cared more about stock price than their welfare...i tend to agree. Also....IBM seems to shed a lot of really good talent at the entry level.