It's kind of fun to find some new Mango apps in the Marketplace, specifically ones that take advantage of the new motion APIs that weren't available before. Case in point? Compass by Kanzsoft and fetches for a modest $0.99 (no trial though).
As to be expected, it prominently warns you that this "uses features your phones doesn't have" specifically hardware for the compass (Dell Venue Pro here). Still, you can buy it!
So what happens when you run it? An error message reading "Compass not supported on this device" at which point the app exits. Ta-da! So be warned, that app really truly won't run on non-Mango devices, at least not without some OEM APIs first--so heed that official Mango update (thanks, @Cyruss1989). We suppose if any of you have an HTC Mazaa or Toshiba IS12T, you could give it a go though...here's the link!