It's very simple compared to other products out there.
We use Pentaho for data integration, but also PI to implement data mining. That has improved the intelligence behind the data. So, we are able to provide our customer with the ability to understand their data. Our customer produces terabytes of data, so arranging the data, cleaning the data, on data integration, aided our customer to understand the data to improve their business.
One thing that I don't like, just a little, is the backward compatibility. I used Pentaho from version 4, and version 6 does not work with the whole ETL design. So backward compatibility is a problem.
I have worked with this product for seven years.
It's a stable product. In fact, contains some mocks, where you can write your own Java software, and do an ETL, specific for your needs.
The support is very fast, but there are also a lot of forums to address problems, so you can find the solution to your issue easily. There is also the possibility to buy support, and when we bought support they resolved our problem in 24 hours.
It was very, very simple. I copied the integration folder, started the tool to design the ETL, and it worked. Time was required to design the ETL, just to understand how each block works. So, when you understand how each block works, you need spend no more time to use the product.
Before using Pentaho, I analyzed other products to understand what is the best ETL product. I tested Talend and Oracle Data Integrator. Oracle Data Integrator is a little bit more difficult to understand, how it works.
So, I preferred Pentaho Data Integration because you just have to drag and drop the block, draw a line to connect the block, write the query, and connect to the DB. There's nothing else you need to do. For Oracle Data Integrator, and also for Talend, you spend more time installing the product. By contrast, with Pentaho, you just have to copy the folder, launch the product, and then you just need the Java machine and it works.
When you start to use this product, if you have just a little experience and know about ETL, you will have to spend little time to learn the it. The product is very, very simple to understand. You can build functionality by yourself.
Anyone thinking about an ETL product, if they want high productivity on data cleaning and data movement, Pentaho Data Integration, in my opinion, is the best tool.