Would you have a look at Vize Software ? (Disclaimer: I'm a cofounder) :)

Looks great for big datasets; respect! A small thing: Why did you decide to bring the "Modifier" panel to the right-hand side of the screen? Lyra is doing the same thing. It results in SUCH a long way to drag your variables. Besides that: Neat tool! Hope you'll be successful with it.

Thank you :) Funny you mention that, we're in the process of wrapping up a UI overhaul, and the modifiers panel is right next to the variables one. Meanwhile in the current version you can also double-click to have your variables added automatically to whichever chart you're on (based on a charts suggestion engine).