Pros
Before an interview, you will be expected to clear a test which is one of the most important parts to get into any of the internship roles at IBM. This test has questions on Verbal Ability (to check your understanding of the English Language), Mental Ability that consists of questions on Logical Reasoning, Data Interpretation and Quantitative Aptitude. On addition to that, if you are applying for a developer role, you may have to go through a Coding test. This test will have logic based questions where you will have to choose from a given set of options or in some cases even write algos too.
Cons
I wasn't hired as an intern at IBM but as a full time employee only. But I do know a few people who were hired as interns too for technical profiles. So I shall provide information based on both experiences in my answer.
