Coming from cameras that don't have stabilisation, it can seem like a gimmick or maybe a useful feature that one wouldn't feel that is overly critical. Now, I can't choose another camera unless it has this magical aid.
To really illustrate how powerful the 5 axis image stabiliser is in the EM-5 I attached my Canon 200mm f2.8 fd and did a quick test. They general rule for a steady image is a shutter speed that is similar to the focal length which would be 1/400 second in this case. I shot the following images at 1/30 second just to see how well the stabiliser works:
ISO 400, f8.0, 1/30 IS off
ISO 400, f8.0, 1/30 IS on
Pretty impressive huh? 1/30 second is pushing it for even normal primes on cameras like the Sony A7. With the Panasonic 25mm, I've been able to get steady shots right down to 1/2 of a second and 1 full second with no tripod, no patience, just snap and shoot. It seems crazy that only Olympus and Pentax make cameras with in built stabilisation and why Panasonic even bothered putting it in its lenses.