We use both DataStage and Pentaho, but I don't see any special features in Pentaho that is not available in DataStage, except Big Data plugins and connectors. These are default in Pentaho, and for those who have expertise in Java and Java script can write their custom code or enhance and call from Pentaho's code.
Improvements to My Organization:
When we wanted pursue this tool, the major factor was the amount of money we could save. Other than that, there is no special use cases for using this product as it was not that matured when we started using it in 2012 when compared to other ETL tools.
Room for Improvement:
It's still not user friendly or robust enough for our needs.
There were issues with the deployment.
There have been stability issues.
We've had issues scaling it for what we need.
Since there are very few skilled people available on the market, we had to risk the project.
Disclosure: I am a real user, and this review is based on my own experience and opinions.
Feb 21 2016