I imagine the value of this feature varies depending on how much email you send. If you only send one or two emails a day the value may not be obvious - if most of your job is email communication this could be a whole lot more impactful.
It is more about how much effort does email take for you. I don't do that much email but find the task unpleasant and more time-consuming than I would like. Letting and LLM give me a first draft to work from based on the email and a couple points I want to make in reply makes the whole process much easier and more enjoyable to me, and I don't have to worry as much about silly grammatical errors or other small mistakes.
I wonder how long it will take for the sort of tone this generates to become the baseline for what to avoid in high-volume email.