I think it really depends on what metadata is being used for to determine usefulness.  As noted, alternate colors for an outfit or MAT poses for hiding parts is where it really shines.  On the flip side, it's outright unuseful at times for when you're trying to "cheat".  Probably the primary example is using M4/V4 skins and posing on Genesis since the backwards compatibility is useful yet if coded right the metadata actually shouldn't show up in these situations at all.