These are 100-percent crops from our test scene. When viewed at full size, the 500 HS is very good right up to ISO 800. Yes, photos do get softer and noisier above ISO 200--typical for point-and-shoots--but ISO 400 and 800 are still very usable. Like other "HS" models I've tested this year, the noise and noise reduction are well balanced so you still get good color and detail at these higher sensitivities. Colors desaturate some at ISO 1,600 and 3,200; subjects look very soft; and detail is greatly diminished. While you might not want to view them at larger sizes or heavily crop them, the high-ISO results should be satisfactory for Web or prints at small sizes.
The f2 aperture is not as effective for portraits. It will soften and blur the background some, but not to the point of eliminating distracting backgrounds. And since the lens starts at an ultrawide 24mm, you can get only so close to faces before they look distorted.
The 500 HS is the only 2011 Elph with Aperture- and Shutter-speed-priority shooting modes. Available shutter speeds go from 15 seconds down to 1/1,600 second. However, the touch screen makes quickly switching speeds a headache due to a fidgety slider.
Color performance is excellent from the 500 HS: bright, vivid, and accurate. Exposure is also very good, though highlights will blow out. The auto white balance indoors is a little warm, but otherwise it's good and you can always take advantage of the presets or manual white balance if you're not happy with the results.
There is some barrel distortion at the wide end of the lens (top), but no sign of pincushioning with the lens extended (bottom). I also noticed some pulling from the corners to the center on wide-angle shots of busy scenes. However, it's only really visible when photos are viewed at full size, and it's not unusual with compact cameras. Center sharpness is very good and is pretty consistent edge to edge with only slight edge and corner softness.
If you want to experiment even more with your photos, Canon's Creative Filters are mixed in with the camera's other shooting modes. These include a Toy Camera Effect (left from top to bottom: standard, warm, and cool), Monochrome, Super Vivid, and Poster Effect (right from top to bottom). You'll also find Color Accent (scene is monochrome except one user-selectable color), Color Swap (replace one color for another e.g. red for yellow), Fish-eye Effect, and Miniature Effect.
(Note: These were taken with the Canon PowerShot A3300 IS, but the 500 HS produces similar results.)