I find the useful scale of a topo map varies with the intended activity. 1:24k is great for hiking, while 1:250k has worked well for driving and wider ranging activities. Years ago, we did a fairly large climb using the only available map, an aeronautical chart. Let's just say it was an interesting experience.

USGS maps are typically dead on with respect to contours, but are often out of date with respect to cultural features. Hiking on National Forests, I often will carry the local USFS map, plus the appropriate topo sheet. Recent aerial photos are often useful as well if you are interested in a very specific small area. With practice, you can achieve 3-D vision of them in the field with no equipment.