I'm have mixed feelings on them, though as they are in the game now I have a mostly negative opinion on them. Basically I think they have potential and even some minor tweaking could help, but right now I think they're too fake feeling and don't add much meaningful - imo. I do like some of the subtle animation/tone changes they have in a certain emotion however.
Happy is a bit too prevalent, and it boosts other positive emotions. Because of that if your sim has a negative emotion it can be easily buried under a slew of superficial happy moodlets, like nicely decorated. This also causes them to switch emotions far too fast, like jumping from sad to happy to playful in under a minute.
Tying into that, emotions are influenced too easily by decor. If your sim is angry from an annoying conversation or sad about witnessing death, they shouldn't suddenly be peachy because the room they're in has a painting and a flower vase. I don't think decor should influence emotions at all unless you choose to make them do so, like items with an emotional aura.
I also don't like how currently many emotions don't affect your sim enough and are instead mostly used to make building a certain skill faster, or how you're encouraged to manipulate their emotions like getting them in a required mood for work, doing an action for X amount of time while in a certain mood, etc.