During our due diligence while looking for an ETL / data integration tool for our vast needs, Talend rose to the top for a number of reasons. Here are some, but not all reasons we have been using Talend for 6 years and will continue to do so in the long-term future:
1) Open Source - we all know the arguements for open source software versus proprietary, but we really needed a solution we can control, and not be at the mercy of an enterprise software's development team.
2) Support - not only does Talend offer really responsive ticket-based service, but the tools are supported by a passionate community. Whether it be a one-off question or a missing component I needed, I've always been able to find it in a reasonable amount of time. There hasn't been one issue I haven't been able to resolve.
3) Ease of Use - once someone gets past the learning curve, the tool is incredibly easy to use and deploy.
4) Extensibility - we love the fact we can deploy, not to multiple physical servers, but to multiple virtual servers on one box... again, full control.
5) Price - Talend was, by far, the best bang for the buck.
* There were idiosyncrasies to deal with in the early days, but with each release, things have actually been fixed.
* Performance - performance used to be an issue for us in dealing with very large files, however speed has been drastically improved in both, job processing and adminstration.
We use Talend in several environments from integrating business partner product information, content and inventory status feeds as well as master data to data warehouse ETL procedures.
The primary benefit has been the time reduction in solving real data problems. What used to take us two weeks (code, debug, QA, deploy), now takes us hours max.