Pros
No doubt that the history of Dimension Data is distinguished and they still have a strong presence with some of the major technology vendors in the market. There are still some very good people there but there has been major churn of people.
Cons
Current Australian CEO and COO returned to Australia following their failed Cloud Business Unit global roles. In the time they were away from the Australian business, their successors had done a lot of work to break the old boy club and culture of fear that they had previously instilled in Australia. Once the CBU initiative failed, they were sent back to Australia and within months the old culture returned. Some great leaders were moved along and the old club returned. If you join Dimension Data you will not progress a career. The old boy club will prevent all but minor advancement. Be prepared to work long hours for average pay and little significant career prospect. Be prepared for a lot of change as the announced NTT integration takes place. Be prepared to be bullied particularly if you are in Sales. If you are a technologist, be aware that DD is very old school. The cutting edge work is now done by other companies. DD stalled about four years ago when they focused only on their homegrown cloud and the industry moved on with Azure and AWS.