• See what's playing, and stop it. Installed Apps now shows a "Playing" badge
  on whatever game is currently running, and the Play button turns into Close
  game so you can stop it right from the app (with a confirm — it's the same
  as quitting on the console).
• More patience when launching a game. A first launch (just-installed, or a
  cold start) can take a while to come up. Pressing Play now shows "Starting…"
  and waits for the game to actually appear before saying it's playing — and it
  won't let you fire a second launch into a game that's still starting (which is
  what could knock it back down). If it's taking a while, you get a calm "give
  it a moment" note rather than an error.