The main reason for ABS is a little incident I had in my old Nova a few years back. The main ingredients were a wet road, and a bit of a hill. Well at least enough of a hill to hide the traffic congestion up ahead. The raining might have also made it a little hard to see. Oh yeah and I wasn't speeding. From the time my head finished processing what my eyes saw, I could have pulled up in time on a dry road, but as it was wet I ended up locking up and spinning 180 degrees. The only thing which was hurt was my pride.
OK, so a bit of advance driver training might have helped me not spin, but looking back I think the spin saved me from hitting the car in front. A better option however would have been to steer into the next lane which had a bit more room. No that's not how the spin started. If my memory serves me right, a slight misalignment started it off and a bit of panic did the rest.
OK, so I haven't done that in 7 years since and in the 10 years since I got my licence, I could count the times I've had to brake hard enough to lock up with my fingers. Even then I doubt I would be counting all of them.
If I look at it from a probability point of view, it's not worth it. If I look at it from a safety point of view, it can't hurt and may one day come in handy.
Moving away from ABS though, I want a 4.0, not a 3.9. No reason. Just personal taste.