Maybe useful if you are letting your kids drive and it would be good if it could be auto-enabed when in valet mode. I guess it would also be useful for people that are obsessed with maximum efficiency.
I think Chill mode is a clever double-meaning word. Yes, it can be for more gentle acceleration as some have said for people used to Camry acceleration and not the instant gobs of torque available in Teslas.
But secondarily (or maybe even primarily, deepening on where you live), Chill mode is also useful for driving in snow and ice where it may not be safe to have too much torque applied suddenly (especially unintentionally) on slippery surfaces. If you've ever driven in snow, you've undoubtedly heard of the need to accelerate (and brake) more slowly than otherwise you might.
Of course, Tesla being Tesla, doesn't name their modes "Snow" or "Ice" like some other manufacturers do, but instead called it the more clever "Chill".
Chill + regen set to "low" essentially equates to a snow/ice mode from what I have understood from my mountain snow driving Tesla friends.
Don't have a Model 3, so not sure, but the Drag Times guy did a timing test for a 100D Model S and it was almost twice as slow in chill mode. If those percentages were maintained than the normal ~5 sec 0-60 of the current LR Model 3 might be as slow as in the 9-10 second range in chill mode. But maybe someone who has a Model 3 and access to either timing equipment or at least PowerTools will weigh in with an accurate answer.
High torque EV motors can be a bit touchy, my wife complains that small corrections can put her and the kids into “bobblehead” mode pretty easily, which can cause carsickness to some. Chill smooths it out a bit, making it less touchy, but you can still get on it if you need to! I’m happy to see this is now included, but I’ll never use it when I’m solo!
I do like chill mode - it takes the rough edges off, and over a day of driving, that can reduce fatigue.
That said, I've found it to be one of those 90% solutions. All is well until you step upon the accelerator (pedal) and there's no there there. Well, there's a there there, but it's an ICE there as there is a noticeable delay before anything useful happens.
So I don't use it for drives during which I know that occasionally more assertive efforts will be necessary. Other than that, it's good stuff, and I'd like to think there's some incremental range increase along with the fatigue decrease over a longer driving session.