Pros
The Work/Life Balance is usually pretty good. Our prescription plan is excellent. When you find the right area to work in, you can have a really good time at work every day and be proud of what you have accomplished. I hear a lot of people from different divisions say that they have GREAT people to work with. People respect you as an IBMer and know that you aren't going to mislead them. There are generations of trust behind you. Generally speaking, first line managers are pretty good and are kind of in the same boat as regular employees.
Cons
Our performance rating system is a ridiculous leftover from when IBM needed to cut the fat. The fat is all gone, believe me! In general, this is a hard time for engineers at any company. At IBM, bonuses and raises are often pretty bad, even when the company does well.... even when you get promoted. When people leave the company, it's rare to back fill their position. In our area, we sometimes don't even back fill with an offshore job.