The Olympus E-30 offers image stabilization by physically shifting the image sensor. The 50D does not – Canon offers lenses with image stabilization, but not DSLR bodies. There's a debate about whether sensor-shifting is as effective as shifting an element in a lens. The clear advantage for sensor-based stabilization is that it's available with any lens that mounts on the camera. The E-30 includes a control to manually set the lens focal length, for using non-compatible lenses on the camera.
In casual shooting, we found the E-30's stabilization system very effective. We don't trust concrete numbers like a “two-stop improvement” over non-stabilized shots, because we haven't seen a controlled, repeatable test set-up for image shake. All we can say is, at slow shutter speeds – 1/40 and below – we got more keepers with stabilization turned on.
Olympus's in-body Image Stabilization module and components
When someone buys an Olympus E-30, they have paid for image stabilization, and they won't have to pay for it again if they buy additional lenses. With the Canon 50D, each lens purchase will involve a decision about paying for or doing without stabilization.