For me, the biggest complaint about not having an ABS off switch is coming from BMW's abs calibration. I have had two BMW's with ABS, a gs650 Dakar and K1100LT, and two Yamaha's with ABS, the Super Tenere and a 1994 GTS1000. They are just calibrated differently. On the BMW's, especially on loose surfaces, when the rear ABS kicks in, it pretty much releases the rear wheel and applies no braking for what seems like forever, not even noticeably slowing the bike down at all for 20-30 feet, really really horrible off road as shown in the video of the GS going down hill. The Yamaha ABS still actually slows you down off road when you stomp on the brakes, unlike on the BMW's. So far I have not felt the need for an ABS off switch off road. On the really steep, gnarly downhill sections, I turn the bike off anyway and ease it down with it in gear using the clutch and brakes to control the decent. Pretty much the only way to do it safely, the ST is just to big a mass to treat like an enduro bike off road.
http://www.yamahasupertenere.com/index.php?topic=2510.msg42508#msg42508
http://www.yamahasupertenere.com/index.php?topic=2510.msg42508#msg42508