I don't need him to be another movie bad-ass, and I'm fine with him being damaged and confused and even immature. But there's nothing intimidating about his countenance, voice, or design. I can see it being intentional (he's just a Vader devotee), but the other problem is that this character is going to be hard (should be impossible) to redeem -- he killed his dad, Han Solo no less! Not sure where they are going with Kylo's arc, but at least they beat him up to presumably make him stronger.
Here's how I would frame it up -- would you wear a T-Shirt with Vader's mask on it? Would you wear a T-shirt with Kylo's mask or face on it? Or what little kid would want to be Kylo Ren for Halloween?