If you will be doing 100% AC time, keep your battery at 40%-80%. Never, ever, ever, do 100% if you will be using it on AC mainly (unless company laptop and you don't care). Also, unless really using it, avoid full discharges as well. 40%-80% is golden range for Li-Ion batteries.
What if I use the laptop mainly on AC, but every once in a while I want to take it outside and enjoy full battery life, which is what a lot of us do, I guess. According to these instructions I will either limit myself to 80% of my battery's capacity or have to plan ahead every trip away from AC, and precharge my battery to 100%, play with thresholds, then set them back to whatever they were. Does not strike me as good use of my time.
You say to avoid full discharges unless really using it. What does "using it" mean? If you are in a situation where you need a full discharge, isn't it "using it", by definition? Perhaps you mean - use AC whenever possible. This I do agree with.
I also don't necessarily buy into the theory that being fully charged or undergoing full / almost full discharges is bad for the battery. In my experience with Thinkpad batteries, I found absolutely no correlation between these factors and battery longevity. What I did find though is that if your battery is made with good cells (Panasonic), it will likely last for years with only reasonable capacity decrease (~20%). If it is made with mediocre cells (Sanyo), it will likely lose about 50% of its capacity about 2-2.5 years after manufacture date (depending on use too), and then continue to degrade from that point. Sony cells I have no experience with, but they seem even worse.
That is of course, barring the possibility that a battery will just die completely due to a bad cell or faulty electronics. This happens too, and again, no storage/use pattern will protect you from it.
And what is the worst thing that can happen? The battery will go bad, and you will spend another $50-$100 on a new one after 2 years? Not a big deal really, considering that most people will have either upgraded their laptop or spent 10 times more than that amount on junk/gadgets during those two years anyway.
Too often with these advice on how to prolong battery life, I feel that people lose track of the fact that our tools should serve us, and not vice versa. Everyone would want his battery to be "like new", and everyone would like his laptop to stay "mint", but if you buy those things to use, and not to display in a showcase, it's just not possible. "You can't eat the cake and leave it whole".