Looks like Super Stardust HD is getting an expansion pack. You’ll see the download (for £2.49) on the UK store, and the description gives it all away: New game modes, split screen co-op and versus, music attack, ship editor, clan support and better music and graphics.
Don’t purchase the pack yet, mind, because it doesn’t work and you’ll have wasted your cash until the download becomes live. Still, nice find, eh?