Most of it is done with analogue (especially modular) synths. They also used an ondes martenot extensivley on Kid A, which is a sort of cross between an electric keyboard and a theremin that was intended for orchestral use. In some ways they are looking back 30 years or so to a more "organic"...
From the tracks I've heard from the Spain concerts from last year that'd be a good description, although I think they learn a bit more heavily to the guitar driven sound of OK Computer. I'm looking forward to hearing the studio versions of these songs.