I have been involved in testing and developing ABS systems, and have tested cars with and without the systems on roads and proving grounds. There is NO QUESTION in my mind that they are valuable and can help even an experienced driver in virtually all situations. There are some corner-cases, however, where an experienced driver could outperform a system and and there have been some reliability issues. I would still defer to using one versus just disabling it altogether. It would be nice to have a button to disable it as most traction control systems do, but I'm sure that would get overused my the typical driver, when they are the ones that need it most! YOU could always setup such a button on your car, so that it disabled the system until the next key cycle.
One place I know was an issue is when you're going downhill on the sand dunes. With an ABS system, the wheels won't lockup and buildup a pile of sand in front of the tire to stop the vehicle, whereas a locked up wheel would. Pull the fuse before you get out to the dunes and put it back in before you hit the road.
I ALWAYS use my seatbelt, so much so that I've put it on just to move my car to another parking spot. Not that I needed it in that application, just so much of a habit. I also make front seat passengers wear them, regardless of the law. Why? It keeps you (and them) in the seat so the driver can actually continue to drive the car or maintain control when "whatever" happens. If the driver swerves to avoid something and the passenger ends up in your lap, you'll have a hard time recovering.
