We have some experience with KT tape, too. I think it's usefulness depends on the part of the body it's used for, and if there is a way to wrap it so it assists the body part. For example, since it is easier to wrap around a limb joint, there is better chance of supporting that joint in a useful way. I tried it once on my SI joint (in the lower back, where the tailbone joins with the hip bone) and it just wasn't effective for me- perhaps it was an application error, but I really think it's because there is no way to get in there and support that joint.
My daughter uses KT tape for her foot arches during practice, which really helps keep plantar fascitis at bay. She uses the cotton-based KT tape (not the "pro", completely synthetic type). She finds the cotton-based tape to be more supportive of this particular part of her body. It also seems to stick better. She wears ankle braces over the tape, which keeps it on better, as well.