When I was learning to get involved at Apache, Dion was particularly encouraging to me. He was the first guy I met in person from Maven and Apache since he organised the Sydney Java User Groups that I started attending around the same time I became a committer.
He was the first chair of Maven when it became a TLP, and did a significant amount of work on Maven 1.0. Even after having moved on from Maven more than 3 years ago, he remains the 4th largest code contributor to the project, and we wouldn't have come this far without his efforts.
A genuinely good bloke, he will be greatly missed.
Dion's exemplary work at the ASF has touched, and will continue to touch, numerous people and products. Having worked with Dion on one of the projects at the ASF, I was always impressed by his technical vision and ability to welcome and mentor new contributors. Dion was one of the kindest souls around -- I remember his "we're lucky to have you" personal email when I joined the ASF membership, and many other occassions where he was similarly and extraordinarily supportive and gracious. He will be sorely missed.
Dion was a very dynamic committer... together we shared fun of Apache Jelly and tried to shape its rubbery aspects.
Dion's initiative were always striving for quality and I really appreciated working with him.
The announce of him disappearing is a shock for me. We'll miss him.