Over at the Digital Photography Review's Canon Talk fourm, technicsplayer tells us how to turn off the info icons from the PowerShot S1iS's EVF (electronic view finder):
1. Set the modal selector to P.
2. Switch the camera to Replay mode.
3. Switch back to Record mode.
4. Hold down the Up button on the 4-way controller for about 5 seconds.
The info icons in the EVF disappear, except for the Image Stablizer and Manual Focus icons (if those options are turned on).