I periodically do hard braking just to keep the brakes clean, for practice, and because it's pretty fun. I never have any problem getting the ABS to kick in, which means that I'm at the limit imposed by the tires. Which means that better brakes wouldn't improve the stopping distance, even if they made the pedal feel like it was more responsive.
If you never use the brakes, then they glaze over and don't work all that well. That's also going to be true with other brakes. You just notice it way more in the Roadster (and presumably Model S) because of the strong regen.
On the other hand, lots of you who seem to know what you're talking about hate the brakes. So, am I missing something, or is it really just about the pedal feel and not the stopping distance?
- - - Updated - - -
Oh, and another thing that I don't really understand is why if they're planning on putting in something like the Model S power train (better inverter, motor, battery cells) why you'd expect better performance with a smaller pack. That's certainly not true with the S, the larger packs do better. Presumably this is because they have more power, which means that the place where the torque curve hits it knee is faster.
Why wouldn't that be equally true on the Roadster?
Now, if you're trying to build a great track car, maybe the reduced mass would be worth more than the increased acceleration because turning and breaking performance matter more than speeding up. But, I'd expect a larger Roadster pack would have a better 0-60 than a smaller one (until it hits the limit of the tires).