Many of the photos I've taken in low light situations seems to have what looks like red or green dots on them in random locations.  I thought these were "hot pixels" resulting from the longer exposure required for a low light picture.   I also thought this was a sign that my camera's sensor was becoming defective.

After doing a little research, apparently these "hot pixels" are actually "stuck pixels" as found on a Flickr discussion regarding this topic:

Stay away from Pixel Mapping unless you have DEAD or STUCK pixels...

Pixel Mapping is NOT for hot pixels...

DEAD pixels are ones that no longer work, and would result in a black dot at the same spot on ALL images.

STUCK pixels are ones that are stuck on and would result in a colored dot (usually always the same color) in the same spot on ALL images.

Those are the ONLY pixel issues that Pixel Mapping will resolve.

I think I read that Olympus recommended that you DO NOT run pixel mapping to often as it could result in good pixels being mapped as bad, and once a pixel is mapped as bad it is turned off and can not be turned back on (at least not by the user).

I addition to being able to remove "stuck pixels" through pixel mapping, a feature I never used on my camera was the noise reduction.  A F.A.Q. section on the Olympus web site explains how noise reduction works on the E-500 and how to turn it on:

How does the EVOLT E-500 combat noise commonly found at high ISOs?

My online search seems to show that hot pixels and/or stuck pixels are just part of the dSLR world and having a few spots on one's image isn't justification for throwing-out one's camera.  Between using the camera's pixel mapping and noise reduction, or through manual photo processing, the hot pixel issue is one that I have to learn to live with but can fix.

Another cool tip found on the Flickr discussion group was how to get use data out of my camera, such as how my pictures I've taken with it:

Hot pixels is normal on almost every SLR camera and can be removed quite easily.

I would be more concerned with shutter activations because that is a major mechanical part in the camera that can go wrong.

Apparently, Olympus guarantees the E500 for 50,000 shots. I’ve taken 61,565 shots and there is no sign of failure but I’m ready to accept a problem!

If you want to check the usage stats on a E500 follow this procedure…

1. turn the camera on
2. open the memory card door
3. press “play” and “OK” at the same time
4. press the following buttons in the following order - "up" "down" "left" right"
5. fully press the shutter release button
6. press the “up” button
7. press the “right” button – takes you to page 2

On page two you will see…

R: wwwwww – how many times the shutter has fired
S: xxxxxx – how many times the flash has fired (includes hot shoe flash)
M: yyyyyy – number of times mirror lockup has been activated
U: zzzzzz – SSWF count - number of times sensor cleaner has been activated

My E500 says:

R: 061565
S: 014403
M: 000088
U: 008833

If you shoot RAW then isolated pixels aka hot pixels is an easy situation to deal with. Lightroom and Photoshop ACR will automatically remove them for you and other RAW processors will give you an option to remove them.