First of all I should say that I bought this to use with two keyboards, so I am not really in the target market. The unit is designed by Source Audio a manufactuer of effects pedals that are targeted at guitarists - it's intended to be used with their products (hence the special extra connector), but you can also use it as a "normal" dual expression pedal.
In general looks and feels like a solid unit. Steel case, professional feel. Doesn't slide about, good rubber foot grip.
The unit worked directly with my Roland FP-7 Stage Piano and would probably work with other Roland keyboards. For Korg you need to build a special cable, reversing the ring and tip - I did this and it also works.
There are no switches to change type or reverse polarity, but this is also fixable by creating special cables if you need to.
Few wierd tihngs -
It comes with one(!) 1/4" TRS cable and the special proprietary cable for using with Source's own products. So this means you specifically went out and bought a _dual_ pedal, but it comes with _one_ cable. That's strange - I didn't really mind because I wanted to use my own cables that are longer, but packaging a dual pedal with one cable seems odd. The supplied cable is about 1m - fine for patching a pedalboard (which is the intended market), not really long enough for keyboards.
Next thing - the sensitivity control only affects one of the outputs. In my case no problem at all, but something to be aware of.
The sensitivity knob looks and feels a bit fragile and it sticks out of the side of the unit. Likely to get damaged - or just moved, whereas other pedals have this recessed because you usually want a fixed setting. I don't really mind about this because I don't need this knob - if it broke I would just short-circuit it inside, but not everyone is handy with a soldering iron. Tip to Source Audio - if you ever redesign this thing, then make this knob recessed.
By the way, it is totally passive. On one forum someone said it needs batteries. It doesn't.
There's not a lot of choice in the world of dual expression pedals - this one seems like the best option to me. The Mission unit is quite a lot more expensive and I can't imagine that it is worth the difference. If you want the reverse feature of the Mission unit just build a special cable reversing the tip and ground at one end - problem solved.
So, all in all, pretty happy with this one, but it's not perfect yet!