Achieving 6 Sigma

I’ve read a lot of great discussions hear and have read many books and completed our own company’s Grenn Belt training 2 years after completing Villanova’s GB certificate.  I am still not sold on the results of Six Sigma projects.  Are there any real world examples of companies that are performing at 6 Sigma?  I’ve spoken with former GE and Motorola people and always seem to get an answer that “depends” on the measurement criteria.  This answer makes me question methodology and suspect that major CYA is in use to save their jobs and justify themselves.  For all of the data crunching and analysis, I really haven’t seen any real world examples that Six Sigma works.  Can anyone share their knowledge and tell me of a real world example of a company that achieved 3.4 defects per million without redefining wat a defect is?  Thank you