Sock, I've read everything I can find on Skyhook and from what I can gather, oalvarez has it pretty much covered.
A bit I might add:
The key to "getting" Skyhook is to accept that the valving can react so quickly that it adjusts as the wheel encounters each bump/irregularity, and the adjustment is done as the bump is being handled. That is the "active" part. The claim is that an adjustment from full-hard to full-soft takes 10 milliseconds, or 1/100th sec. The computer reads axle acceleration and position from sensors and tells the valves at each end what to do.
That's how it does what no passive system (e.g. current tech Ohlins for bikes) can do. Run along in full-soft and hit something very hard and the Skyhook valving firms up as the suspension handles that particular hit, preventing it bottoming out. Run along in full-hard and hit the same something and the valving softens so that you're not thrown out of the seat.
The point (for the computer) always being to keep the chassis as stable as possible within the limits of suspension travel and springing.
Within that, you have the four "modes", set by the rider as with the Ohlins set-up. Essentially, these seem to adjust the feel coming up from the road surface. Sport, you feel all the bumps; Touring, less so; Urban and Enduro, as little as possible.
Within each of these four modes, as stated above, you have the option to further refine the feel level. So when running in "Sport", you can choose from hard, medium or soft. Same in Touring, etc.
Whether Sport "soft" is the same as Touring "hard" etc, or whether all increments in Sport give more feel than Touring "hard", I don't think anybody has worked out at this point.
But even if there is overlap on the bump side, there is still the other aspect of Skyhook, which is its auto-adjusting the damping to resist chassis pitch under brakes and acceleration. How much it does this will be affected by what mode you are in.
Finally, there is the question of rear spring preload. It is not clear whether Skyhook offers the same 16 preload steps as the Ohlins, or whether it is just four steps (i.e. rider, plus luggage, plus pillion, plus luggage) similar to BMW. From early reports, is starting to look like it may be just the four.
I think there is no doubt the Skyhook takes away some control from the rider/owner. You can't take it to a suspension shop and change valving etc. Anything like that would happen via updating the software. And whatever you have set it to, the suspension makes up its own mind as to how appropriate your setting is for the conditions. But as long as Ducati/Sachs has done a good job with the software, that will be absolutely fine for most people.
BTW: Also not quite clear at this point, but at least one press report has claimed that within each mode, you can also set comp and rebound independently - e.g. comp to 'med' and rebound to 'soft' - if you want.
Hope that helps some.