The greatest thing about BlueMix was its promotional budget. Saw The Force Awakens on IBM's dime, and got about $50 worth of movie theater gift cards. All I had to do was sit through a 20 minute presentation about BlueMix case study integrations.
I did look at the BlueMix platform, and it seemed like a big mix of various APIs I could tap into. Some of them looked neat, but I never had a reason to really use any of them.