Although I like my Olympus E-500 for taking photos in daylight, I've been very frustrated with it when taking photos in low light situations. Since it's winter here in Wisconsin, I find myself almost always in low light situations these days and I started leaving my camera at home because I knew that I wouldn't be able to get good shots with the built-in flash.
As with most cameras, the built-in flash usually resulted in a lot of "red eye", unnatural shadows, and over-exposed subjects with dark backgrounds. If I turned the flash off, I just ended-up with a blurry mess (even at high ISO settings) since I rarely wanted to shoot subjects that were not moving.
One thing I really don't like about the E-500 is that is strobes the built-in flash in order to get a focus lock. Not only is this very distracting, especially if the subject of your photo is a person or an animal, but it doesn't seem to work very well since the camera doesn't get a focus lock very quickly.
After attending a wedding a few weeks back where the photographer was taking one great shot after another in low light, I asked the photographer what his 'secret' was. He said that he was just using a 'fast' lens along with the external flash and had his camera set on auto focus. Obviously, there there wasn't anything magic about what this photographer was doing to get good shots, but he did have a good external flash that I did not have. So, thanks to a decent sale on Amazon.com, I purchased the Olympus FL-50 external flash.
Although Olympus offered cheaper models than the FL-50, I decided to get their flagship model because it is the brightest flash offered. As someone stated on the DPReview.com forums, "You can always tone-down a bright flash to make it dimmer, but you can't make a dim flash brighter."
This is the first external flash I've ever owned, so I wasn't expecting to be able to take decent photos for quite a while until I learned how to use it. However, I was pretty pleasantly surprised with how quickly I was able to start taking very nice indoor shots while just leaving the flash in it's auto mode.
Because the FL-50 blocks the built-in flash on the E-500 from popping-up, the flash uses it's own red light to assist the camera with focusing in low light situations rather than strobing the built-in flash. To me, this is a HUGE reason for buying this flash. No more annoying disco-tech strobing and the camera does get a focus lock much more quickly with the IR light.
The other feature I really like about the FL-50 is it's pivoting head. It can be pivoted vertically and horizontally so you can make that the light is bouncing off the correct object regardless of if the camera is vertical or horizontal.
The only thing I don't like about have a flash on the camera is that the camera feels very awkward now because it's so top-heavy. If I'm not holding onto the camera and just have it hanging around my neck by the strap, the heavy and tall flash has a tendency to cause the whole camera to fall over. I suspect this would be an issue with any flash, but is still a bit annoying.
So far, I'm very happy with my purchase. I've got a lot to learn about how to use an external flash, but even in the few times I've used it so far, I've greatly increased the number of successful photos taken as compared to when I was just using the built-in flash.