Flying is rather tricky, as the Google team seems to have invested lots of efforts into the UI (joysticks are supported, for instance) so that the flight instruments are rather "mimosa-like". A test flight using a normal keyboard and mouse ended shortly after takeoff. Here's a list of flight sim commands in English or German.
[robg adds: I've tried this, and it does work, though I'm not sure it's the most accurate "flight" simulation. Joystick support on the Mac works; it saw my Saitek flightstick, even recognizing and using the trottle slider for engine control. In-flight dynamics, however, need some tuning. It is quite fun to zip across the landscape in this manner, though.]

