It's been a minute - good news though, I am now working on this project full-time. Excited to get it in people's SQL loving hands. But to tide you over before some more substantial posts, here is a couple of really cool things I have been working on (plus some screenshots of some test boards).
1 - A better way to access the "on the fly" generated viz recommendations as you slice and dice subqueries (every query you run will likely have some ready for dragging)...
2 - If we have good "base recos" that are fast to generate and browse (and ones that show real data!) - it becomes somewhat less important to have an old school "drag this dim on X, drag this measure on Y..." kind of interface (yet it does exist, of course).
But what you can do - is drag in a viz reco that looks reasonable and THEN tweak the assigned fields and browse you options deeper. I find that I can draw up almost 75% of things I need to throw on a board this way. The last 25%, you can access the viz code (and subqueries directly and modify away).
More coming, please hit me up on Twitter (err, X), since it's where I post stuff first.