From what I've read around here I've made up my mind that my bike is going to have ABS. Please keep in mind any of this pertaining directly to motorcycles is read knowledge and not personal experience. I only really have experience with cars, wrenching cars, and a little bit of dirt biking.
There is one important thing to remember about ABS. It DOES NOT help you stop faster. It's lone purpose is to help you maintain control of the vehicle by preventing the tires from locking. If the ABS detects a tire locking it will release the brake pressure by a tiny amount until the tire rotates again and then reset itself, rinse and repeat til you stop or let off the brakes. This works great on dry surfaces, it allows you to maintain control of the car while still braking with maximum effectiveness where you might not otherwise do to inexperience or panic. This is a great feature for many drivers and conditions since most people will instinctively slam on the brakes during a crash. The problem arises when you run into a deformable and\or slick surface such as ice, gravel, snow, mud, ect. In these cases you can stop far faster by locking the tires and letting them dig into the material and form a pile of it in front of the tires. ABS will try and keep the tires spinning and stop the car with greatly reduced effectiveness. My car does not have ABS and I've driven plenty of other cars that have had it and I can tell you without a second thought I'd rather be driving my car in the salty slush they call snow up here. I've also practiced with it enough that I know how hard to brake in most conditions while maintaining control of the car.
This all holds with bikes. You can generally stop faster on pavement without ABS if you know what you're doing and can always stop faster without it in mud, dirt, ect. The trick is knowing how much brake pressure to apply. Every car I've owned so far has been without ABS and I've learned to brake correctly without it. This takes a while to learn and I've locked my car up and sent it spinning more than once. It takes even longer to override your instinct to slam on the brakes as hard as you can. The problem on a bike is if you lock the front tire on pavement you may end up in the emergency room and your wallet definitely is compared just ending up in the ditch. In gravel or mud this is still a problem but you are usually going much much slower and the lack of friction gives you time to react if your tire locks. It is actually beneficial to lock the rear tire once you're going slow enough and let it drag you to a stop, releasing it if the rear end kicks out too far.
In short learning to brake with maximum effectiveness on pavement takes time and you will likely go down once or twice. On pavement ABS allows you to do this right out of the gate with no experience and doesn't care if you panic and slam on the brakes as hard as you can. On gravel, dirt, snow, ect, it is detrimental and dangerous to trying to stop quickly and you must stop by properly using the brakes and bike. It's also less dangerous to lock a tire in gravel because you're usually going slower and there is more time to react before you end up horizontal.
My Strom, when I get it, will have ABS and the first thing I'll do is add a switch to turn it off when needed. When I finally end up with a car that has ABS it'll either end up disabled or have a switch to turn it off. My opinion is I wouldn't ride a street bike without it in large part due to my lack of experience and high probability I'd slam on the brakes as hard as I could in a crash.
Hope this helps,