Ease of use, clever transformations and in general Centerprise has a library of transformations that even heavy duty tools like Informatica doesn't offer, such as SCD.
You can literally be up and running in a few seconds, with a very low learning curve.
When you have to move millions of records, the tool doesn't perform too well. In fact we discovered that the more transformations you have, the slower it becomes. Because o this we replaced many of our transformations with source SQL. Either you do this, or you use their Push down optimization (PDO) capabilities, but this only works within the same database type.
I also don't like their licensing model. They seem fixated on charging per customer, instead of having some sort of server-based license with unlimited users, like Informatica, Yes, they will give you bigger discounts if you buy more, but this is an ETL tool, not a reporting tool.
This tool is incredibly easy to deploy, learn and use, but be prepared to fine tune the heck out of it to get decent performance if you have huge data volumes, Use PDO when possible.