Not to forget the one fairly common circumstance where ABS hinders - packed snow and ice where you do need to think about it. ABS can significantly increase your stopping distance.
This is absolutely correct. If you are driving on a loose service (not just _packed_ snow) like snow or gravel, emergency braking is faster without ABS because skidding the wheels causes the material to bunch up in front of the wheels, dramatically reducing vehicle speed.
On a constantly slippery surface (ice, snow, not normally gravel) you may want to disable ABS because the ECU cannot correctly tell the vehicle speed, so may activate ABS incorrectly. However, modern systems to tend to be quite good. I believe it is best to keep systems such as traction control on though.
I learned to drive in Colorado (plenty of snow and ice in the winter), where I was a poor college student driving a typical poor college student car (old, beat-up, no modern safety features like ABS, etc).
Now that I can afford to drive a reasonably modern/safe car and live in Florida, I still can't bring myself to not instinctively pump the brakes when making an emergency stop.
A common belief is that ABS always makes braking better. That ignores the situations where it can make things worse and you should probably turn it off.
It's not simply a question of excess speed. One very common situation is where housing estate minor roads have ice or snow, but other routes are cleared or gritted. Most would probably drive in that. ABS can leave you with nearly no braking and in a far worse position than if you'd just turned it off. You might be moving at 10mph or less but slowly sail, with no control, from the minor road into a major road at a junction, or into parked cars.
