Before I had roughly 20-30 downloads per day, now that it's spotlighted it's between 250 and 280 a day. The conversion rate is a little over 28%. Note that this is for an app that's only available in Dutch. I have no idea if it's visible to people who don't have Dutch as a fallback language or however that works, but the description being in Dutch I don't suppose many of those downloads are non-Dutch speakers. Also it's somewhat specific in its target audience (people who shop at that particular Dutch retailer). For an OS that's been out three weeks or something I'm kind of impressed.
The hardest thing, I've found, is getting people to rate the app. I have four ratings, and one review. Even people I know and have asked to leave a review or at least rate the app simply refuse to do so for some reason. It's baffling and a bit annoying, since I'm guessing the number of ratings/reviews count to your "noteworthiness" or whatever the default sort method for the store is.
I've made a bunch of sales through the app, but I suppose the real test will be the holiday season. And then the real real test will be next year's holiday season when people who got their W8 devices this holiday season use them to shop for that holiday season.