The great thing about using a limited palette is that there is a lot of unity in your work because every mixture contains all the colours used. It's the main reason why I also use a limited palette. It varies, but usually contains a blue, a red and a yellow + white. Sometimes I add one colour to be able to mix black (eg burnt sienna when my blue is ultramarine, or phtalogreen or viridian when my red is alizarin).
I gotta admit I've not tried the 2 colour (and I assume + white) yet.
It sounds very interesting to say the least.