I get that people want this life stage, but personally I would rather that teens be more like teens. They did address some issues in the HSY with crushes, stupid challenges and their own aspirations, and they do have their mood swings, but left to their own devices a teen will cook, clean up, do their homework... all autonomously. They're more like a parent's dream of a teen than any real teen. I want slamming doors and arguments and hanging out with friends on the floor while blasting music and throwing clothes on the floor even if the hamper is 'right there' and refusing to make the bed or clean up after a meal. That would make them stand out.
What I do miss is a middle aged life stage. They added some of this with midlife crises (love them) but I still get adults having babies a few days before they age up to elders. A life stage with thinning hairlines, drop in fertility and wrinkles would be nice. Or maybe just a gradual drop in fertility (and desire to have kids) in adults so there is some changes in an adult sim's life.