Looks pretty neat. Having not fully investigated it yet, I will say the one thing I usually run into with this and other BI tools is a lack of flexibility in the UI for forming queries. It's sometimes limited to one table or view at a time. I wonder why more of them don't use more flexible querying techniques, perhaps just due to the risk of a bad query being formed?

My preferred approach is implemented in Zillion, which I use for BI at my company: https://github.com/totalhack/zillion