Vantaggi
IBM is a big company, of course! And it really depends in which part/division of IBM you are working and what your mindset and expectations are. The trainings are really good and you will have a great chance to explore different projects and technologies within your country or even in different countries. It's definitely a very good place for graduates to build up their experience and their CV/Resume. If you like to work in a big corporate and don't mind a bit of politics then go for it. I have seen many people who joined IBM as graduates, stayed there for couple of years then left IBM with a good experience and then after 20 years or so they are back to IBM with a very senior position to end up their career with a safe job and good money. You need to build a good network of good people in IBM to be able to survive and work in good projects.
Svantaggi
As said it's a big company and although they claim they have been re-inventing IBM but they can not deny the fact that the company has a strong and old legacy which can not be changed quickly and can not compete with much smaller and dynamic companies . You can't expect high salary unless you are at a very senior level. If you have an Entrepreneurial mindset then you will not enjoy working in IBM unless you are in a unique project. If you are going to work in the consultancy wing of IBM which is called GBS then good luck with finding a project. If you finish one project then IBM does NOT assign you to another It's you who have to find a new project and go for interviews etc. Almost like looking for a new job. This is where your links can help you, otherwise you have to stay at home (still paid) for sometime till you find a new project. If you do a fantastic job no one would come and tell you that you are promoted. You have to prepare a promotion pack yourself and you have to 'BEG'. If it's your style then you are welcome. Politics play an important role in EVERYTHING in IBM. If you are not that person then don't even come closer to IBM. Overall, it really really depends on your luck and the country your are going to work for IBM and the division of IBM that you will work for and the people in there. And be careful, if you are too goo you only find jealous enemies who feel very insecure by seeing you doing good.