Vantaggi
If you are newly hired as an experienced professional, you can get decent pay. Only don't expect adequate pay development or bonuses. Technical community is strong and still well-skilled - but without adequate training, that too will change over time.
Svantaggi
Corporate culture has gone down the drain in the last few years. The old IBM value "respect for the individual" is gone. New values are payed lip-service at best. Jobs are being cut and relocated to offshore countries, but the company is very skillful in keeping that under the radar. IBM Germany has never made a loss in the last few years, yet there still were pay reductions. Management constantly finds excuses why pay rises and bonuses have to be sub-standard. Individual performance is hardly taken into account when it comes to compensation, and internal employee ratings are based on a Gauss distribution per department, effectively screwing some people in good departments. In the past, IBM would seldomly boast about how great it is, but it was. Nowadays, even the Intranet homepage is filled with marketing messages, yet the employees are kept in a constant state of pressure and fear of job loss.