The "Discernatron!" title should probably link back to the main page.
<nitpick>It could also be little bigger, and not gray on black.</nitpick>
The big login button should be more of a call to action than just "login"
Can the rankings be either buttons or radio buttons - not both? It's a little unusual that I can click/tap anywhere to change the radio button status. Rather easy to goof up and click the wrong row. Maybe if each option (Irrelevant, maybe relevant, etc.) were each a button that could be clicked and would turn the appropriate color. Not one long bar.
I agree that the title should link back to the main page, and it could be bigger. I like the color scheme though.
What more call to action would you suggest? I don't disagree, but I can't think of anything better. It's nice to know that you are going to have to login via meta, and the ginormous "Search needs your help!" is already attention-grabbing.
I started on the talk page rather than the article page, so I'm discussing this the wrong way round—sorry. I prefer the current "Login via meta.wikimedia.org" to "Get Started", which is too generic, and doesn't strictly apply when you come frequently.
The UI is unusual, but once you get used to it, it's great. I try to do one or more queries most days (though I don't always succeed) and I really like the UI now. The original intent, as Erik has said a few times, was to make it easy on mobile—so you can do queries on the train, for example—but I've come to like it on desktop.
