well, this really depends on the type of modeling that you do.
i was recently doing some level building and i had a fairly big scene, i had dynamics i was working with.
the problem is i scale duplicated a lot in -x direction, i also did a lot of combines with a lot of arbitrary objects without checking normal direction of certain objects, so i ended up with poly bojects with normals pointed in every which way. {by combine i mean for instance if u have 2 simple sphere one with normals reversed and other with normal at default, then you combine them, now u have a poly object with odd normals, so if u are doing dynamics calculation on thta poly object the one with the normals pointed the right only those faces will get calculated [per say].} so i needed a way to find which way normals were pointing in the scene for any given object at any given time.
and i had a huge amount of objects. i guess this isnt really a problem if you just have a single character you are working with. this script i posted helped out a bit.
--------
to see how this thing can tick you off, create a simple sphere; select bottom half and reverse their normals. then in object do editPoly>normals>conform.
and watch how nothing happens.
if it worked correctly it was supposed to at least put all the normals in the same direction [which ever way], now imagine if u have 100 of these spheres in a scene.