Right now the volume controls are potentiometers. Absolute analogue resistive scroll thingamabobbers. The have a finite spin, and come with a little knob. Knob is ok, but I prefer the 2 for $3.99 pack of stainless steel knobs at RadioShack for them. They work 100%, but are not what most people are used to. If you have used equiptment from the 80's or early 90's where you could only spin the wheel so much and then it stopped at a maximum volume, that is what this is. (Same with the linear)
What is under development right now is using a digital encoder. A infinite spin knob such as what is found on a modern stereo. You can spin it (to quote from a favourite 80's song) "spin me right round, baby right round, like a record, baby right round round round" forever.
There are those that hate both. Some of the older people like the feeling of a knob that they know what the volume is by looking at it because angle X is always volume Y. Whereas todays generation including myself prefer the infinite spin where you cant tell the volume by looking at the knob, but usually looks much cooler.
So to sum up, yes they both work. But are not digital encoders, they are analogue potentiometers.