Good luck finding the case studies. I've read a few good ones over the years but a lot of unbalanced sales-brochure like testimonials.
UML is an important specification and can be very useful when used to help with the design phase of projects.
What vendor case studies won't mention is:
UML requires a large amount of write-off in current training investment as programmers become application modelers.
UML/MDA requires new development routines and practices.
UML and MDA is often sold to management and imposed on
Java developers, which is one of the reasons why MDA has met with strong resistance from Java developers.
UML/MDA tools vendors tend not to provide the source code and often demand expensive professional services fees to modify or customize the tools. This can result in expensive professional services for customization.
UML/MDA model evolution maintenance requires tedious, repetitive, manual intervention. The modeler must ensure that the UML model reflects changes for every major and minor change.
UML/MDA model implementation involves the time-consuming and error-prone tasks of manually mapping a UML model to platform-specific code.
Java developers sometimes resist the introduction of MDA products because they are often introduced and used by business analysts, thereby putting the position of Java developers within an organization under threat.