To me it feels rather useless for the main reason that the traits and aspiration are locked. I think it would be a very useful starting point to create sims if I could tweak their traits a bit more after the quiz.
I can see myself using it for background characters / extras in my stories but I prefer full control on the creation of my main sim. I will keep using cheats if I want to change their starting conditions. Although most of the times the cheats I use are meant to reduce starting money and delete skills from gallery sims.
If maxis unlocks the traits after the quiz and I will change my answer to useful and use it a lot.