If you've known me for any length of time, you know my love of and heavy use of open source. Rarely though I'll find tools that aren't pure open source that are quite worthwhile to have in the toolbox. For a long time, my main go-to data integration tool has been Pentaho's Data Integration (aka Kettle aka Apache Hop). Another long time member of the Kettle community (@slawo) has been working for the past year on a new modern data integration tool called Tweakstreet.
I have been using Tweakstreet exclusively for the past few months to really kick the tires and have to say it's an awesome tool and coming along (and I would argue, surpassing) feature parity with many of the other big name data integration tools including Kettle.
I'll be adding some blog posts with some tips and tricks I've hit that may be helpful for others who want to start playing around with it. Go ahead and check it out - there's a unlimited trial going on now and if you do go for a license, they are quite reasonable.
Open Source backing
Now another factor about Tweakstreet that I'll mention here is Tweakflow, an open source embeddable scripting language for JVM and used in Tweakstreet. This can be used in other tools and is pretty powerful on its own.