Saw a couple of GoF2 ?s:
Control ship speed (0%-100% speed) by swiping up/down. Protip: Swipe left/right for a nifty evasion move that is a life-saver once you max out your level and are facing swarms of kitted out enemies.
Minimizing real-time tedium: If you are not in combat and are locked on to an appropriate target (space station, jump gate, waypoint) a fast forward button appears on the HUD which doubles or triples the passage of time. Combine with a high level speed booster for super-fast transit. (FF button also speeds up booster recharge rate accordingly!)
Looting: get a tractor beam. High level enemy pilots can drop pseudo-über loot that sells for a ton of cash. Even random, incidental encounters can net you tens or hundreds of thousands of credits worth of loot between runs.
GoF2HD: It's EXACTLY the same game as vanilla GoF2, to the point where they even share the same set of achievements. I got 75% of them them with my iPh4 while playing the vanilla game, and quite recently got the rest on my 4S after I started a new file in the HD version. Essentially, only the graphics and bugs have changed. GoF2HD does not come with free DLC. However, if you purchased the Valkyrie expansion in vanilla GoF2, and have since upgraded to the HD version of the game, then you will be able to download the Valkyrie HD expansion for free. The Kaamo Club unlock key does not transfer, however.