Is it worth the extra money for a lens with image stabilization?

I recently purchased a 50mm f/1.4 prime lens for my Canon to complement the kit zoom lens. I initially figured the wide aperture would make it great for shooting in low light without flash. I did not consider the fact that the 50mm lens does not have image stabilization. After a couple of hours using the "fast" 50mm lens, I quickly realized that I still need about the same amount of light to get sharp handheld shots as I did with my f/3.5-5.6 kit zoom lens. The difference is the image stabilization. With the IS lens and a motionless subject, I can shoot at much slower shutter speeds without any noticeable camera shake in the final image. Therefore, for me, the image stabilization is a feature that I must have, especially with a telephoto lens. Combine IS with a fast lens, and you have the best of both worlds.