After using over-emotional a lot I’ve noticed the following:
It boosts mood, and keeping the mood bar full without it is not that hard. So is it worth it?
Generally I start on an empty lot for the vista moodlet, and get decorated for the bedroom right away. Sims spend the most time in one single spot in bed early on, be it rabbit hole or even self-employed Sims. Then find a recreational activity and the sim is set for full to very high happiness almost 24/7; over-emotional or not. Based on job/profession I work on decorating the next prime area. Especially with professions/work activities that are fun like guitar, painting, etc.
Keeping mood high is not very hard and once the bar is full, any bonuses to mood will not make a difference.
With the ambitious trait, regardless of job or mood you will always get a bonus to LTH points. Which affect how fast your sim accomplishes things more than mood.
I also remember a post of Pam’s (can’t find it right now) where her sims without over-emotional also earned just a touch more than those with the trait.
Unless I’m missing something?