I like that this particular hybrid meant I could take the hair color from Sarah and the waviness from Grace as opposed to just another two-color situation. I like having options, darn it.
This spell, in my opinion, has great impromptu disguise potential. In a crowd and need to look different? Quickly select two people at random and get a result nobody will recognize. Granted, the description says nothing about adjusting clothing size, so MAYBE try and be selective about who to mix together.