I've been using this project with Vertica and it is excellent. It supports Groovy out of the box so you're not constrained to writing extreme SQL for everything - this is an extreme boon over others. Not to mention the ridiculously full feature set. Also the devs are active on the forums - 24 hour response time. Needs some work on completed translations (into english!).
Thanks for the really extensive open source bi solution! We use a reportserver in a trading company and our users love the dynamic list because they are flexible and easy to use.