Actually, for just looking at things under the car or down recesses, as mentioned, it works quite well- The narrow beam actually aids in those situations, because you don't get the glare off the foreground objects, and is pinpointed at the area of interest. If however, you don't know exactly what you need to look at, it wouldn't work as well, because then you'd have to sweep it around.
And, as is the case with any handheld flashlight, if you actually need to WORK on the car, it's not really that good. For a breakdown light, you might want to augment your collection with a headlamp; it'd work better than ANY handheld, megabeam or not.