What helped me and the Wii when it comes to aiming, since I'm lazy, was to just game from one of my office chairs. This way I could rest my arm on the arm-rest, instead of being required to constantly hold my arm up. It also provided a stable platform. This same lazy setup would help out with Sony's new controller.

For games like Metroid Prime 3, I'd move my entire office chair slightly when exploring, to move my field of vision -- which was me being really lazy, it only required a bit of foot movement to do so. Then when the action picked up, I'd use my arm, but still kept my elbow on the arm-rest as a pivot. This allowed me to game for hours on end without my really weak gaming-arm tiring out.

Bleh, if only developers had supported the PS3's dam mouse option, I would have bought one to go alongside my Wii and PC. But noooooooo...