Played a game on a Missile Command / Centipede arcade machine at the Google GDC Party. The trackball takes some getting used to, it would probably be easier for me to play with a mouse.
Got the score 9620 in MAME.
Definitely easier with a mouse.
Got the score 18730 in MAME.
Using the new company USB trackball, I played some Missile Command. Setting the input sensitivity in MAME low enough is key, so fast movements don't 'roll over'. Sensitivity around 20 seems to work OK.