I do wish people would stop rabbiting on about the track when we're talking about something meant for the street. I've never activated the ABS except to test it. If you're clumsy enough to activate it, you probably need it.
If you're using your brakes on the street to the point where you're outbreaking the ABS (and most of the time, in less than perfect conditions on a less than perfect surface you can't, whatever you might wrongly think), then you're already three quarters crashed if there's traffic around.
The extra weight is a couple of KG, set low in front of the swinging arm where it has negligeable effect on anything. With the fuse pulled the entire system is by-passed, apart from the extra length of the brake lines. I don't like having to pay for things I don't want, but I'm ambivalent about ABS - it's a useful insurance policy for when you screw up.
I don't understand the comments about margin of safety. Most systems only operate when there's a measurable discrepancy between front and rear wheel speeds. If you're braking and there is such a discrepancy you're doing it wrong. If you're deliberately overbraking the rear to slide it then you may have a problem, but that isn't a good idea on the street.
I have seen a couple of systems on scooters in conjunction with linked brakes where there's a measure of servo assistance as well as the ABS, and the components of the system can't be separated. I'd avoid anything like that.
If I can ask a question of these track riders - if you're so good, why aren't you winning GPs?