I've spent almost the last two years driving 2000+ miles/week in a vehicle with adaptive cruise control (over 150,000 miles total). In the environment that I was using it, I found it a useful and beneficial technology in many ways. However, the one glaring issue that I found with the technology is that it is very easy (nay, almost inevitable) to be lulled into a false sense of security. The likelihood of getting mentally lazy with adaptive cruise is a real thing, and is dismissed at the rider's danger.
It's also not without its faults. Current adaptive cruise radars have a habit of losing the fix on vehicles under certain circumstances. The problem is exacerbated on winding roads, entrance/exit ramps, and smaller vehicles. There's also a significant issue with vehicles crossing the road in front of you, and a resultant action of panic braking from the cruise system. Dropping anchor in a 4-wheeled vehicle is one thing, dropping anchor on a motorcycle when you're not ready for it is quite another. I've had numerous experiences with false cruise locks, improper cruise releases, and emergency braking triggered by the cruise. They're not fun.
My opinion (based on quite a bit of firsthand experience with the current state-of-the-art) is that adaptive cruise is one of those technologies that can be done on a motorcycle, but maybe shouldn't be done. I predict that as the technology becomes available on motorcycles, you're going to hear anecdotes of riders crashing because of cruise behavior that they weren't expecting. Add to that my personal belief that BMW has some of the least reliable electronics on the road (along with KTM, who are also developing adaptive cruise technology), and there's no way that I'd spend money on a motorcycle with adaptive cruise control at this time.