I've got one I'm trying to get rid of pretty soon. It's a great unit for quick jotting but for serious simple, precise sequencing I love the MPCs.
The best place to learn about the ES-1 (and the rest of the Electribe series) is the yahoogroups board, link here:
http://groups.yahoo.com/group/electribe
Try picking up an RC battery and charger, you can make it totally portable.
I wrote up directions for attaching the battery on the list, do a search for ES-1, battery, and maybe goddamnbastard2001, my name on Yahoo.
-tank.
You don't know what I know
Cuz you aint seen through my eyes
This spliff is always lit but it's a natural high
http://www.dcbeats.net