Most significant Android apps look "okay" on tablets these days in the sense that they are using Android layouts and the icon bitmap dpi system so that when they are scaled up to tablet resolutions they look pretty good, but outside of Google's own apps, very few of them are really "tablet optimized" in the sense that they make extensive use of dual-pane fragment-style UI concepts. Generally they are just bigger, decent looking versions of the single-screen-per-view UIs as seen on Android phones and they feel like that, which isn't horrible, but isn't really taking advantage of the larger (usually) higher resolution displays Android tablets have over phones.