Pros
The atmosphere at IBM is relaxed and casual. This means that you can come to work dressed in jeans and a t-shirt and don't have to wear a suit and tie. Also there are no restrictions on what you view on the internet, unlike at other companies. So if you have time, you can check your mail or other things. You also have access to such things as Books 24/7, which means if you want to learn about some business or technical subject you can.
Cons
Well, one of the biggest downsides is that people are treated as if they were robots. IBM, at least in Bratislava, is one big mess, where people are generally dissatisfied. The pay is low, especially compared to other companies. The benefits are also close to non-existent. It seems as if IBM was trying to save on everything. On the other hand they waste money on other things. The management is pretty incompetent a lot of times.