I think that the main reason for an electronic musician to play live is for
them to explore there musci in a new way and possibly re-interpret it in a
new way.
One of the best live performers I know is Ian Clark of Lessening Lesson. He
has a serios of arpeggios programmed into a few analog synths and a variety
of rythms in his drum boxes. He fades them in and out, mixing on the fly and
in general twisting knobs to adjust the sound. It makes for a long beautiful
trip.
Also, Aphex was fantastic to see, because it was crazy. Vapour Space was
boring because it just sounded so choreographed.
Richie Hawtin is always a blast, if for nothing else to see him curse at his
gear.