I’m always teaching people that the weak link in any small snapshot camera isn’t the image quality, it’s usually the flash power. People take flash photos all the time and the shots turn out ugly from low power, or just the awful placement of the flash by the lens (red-eye anyone?!). I started in digital with some snapshot cameras (still $900 back then!!) and a good flash, and you wouldn’t have known I was using a snap-level camera.
So this is a good idea… a relatively inexpensive slave flash that bounces (shoots light into the ceiling for really pretty, soft light).
I haven’t tried it yet, but there’s not much to worry about. It will fire along with your camera’s tiny flash but with more power and nicer quality. One issue you might have is ‘double flash’ showing, where you can sort of tell by two sets of shadows that you used two flashes. If that happens, just get some little softening material (even a tissue folded over, or some frosted plastic) and use it to make your camera’s flash output enough to trigger the slave, but not so much that it has a big effect on your image.
And for really tough shots like group photos, or subjects a bit away, you’ll never see your tiny on-camera flash anyway (which is why you bought a big slave flash in the first place!).
And it opens up the possibility of creative lighting, but using it as a flash even more off-camera for different lighting effects, as noted here.