I worked 17 years for Big Blue and there is no doubt that the core of ESS, the Spectrum Scale (former name GPFS) is a saleable filesystem. For good reason, it has some installations for High Performance Computing where the required expert skills are available to bring a GPFS cluster up and keep it running. This is typically not the case in commercial environments were IT staff has limited resources and business requires simple to manage rather than complex solutions. I know various customers that have or are in transition from GPFS to Isilon and they all prefer Isilon due to the simplicity for installation and maintenance.