He means the ABS.
I have an 03 reg version, with the servo system. It has done 56,000 without missing a beat. The brakes are like someone sticking a broomstick in the spokes if you want them to be. The servo assistance makes hauling a fully loaded bike down from 100mph very easy - and very much faster than without.
I vote for the servo system, even though I have heard of the problems some people had. However, i cannot see how BMW would leave bikes on the road if there was a recognised probelm. If an accident were to result in a death following these problems and they had not issued a recall they would be in for a corporate manslaughter charge. To knowingly leave machines out there with a common problem and do nothing about it would not be tolerated...BMW are one of the best at recalls. To my knowledge there has been no recall for a servo fault. That means there must be something else that is causing it....a chaffed wire or something from poor routing following service? (I am not saying that is the route cause, just giving an example).
I wouldn't let the servo thing put you off buying a bike. I can't see em getting rid of this one on the next 20 years...I might buy another to keep alongside though. One being done up, one on the road kind of thing. It would be another Adventurer though. The extra height is wonderful and the fuel range is simply a godsend. 300+ miles between fill ups means you can really cover some ground without having to go stupid. The extra long leg of the 6th gear keeps things nice an easy on a long A road or motorway stint.