 Edmunds full expert review has nothing good to say about the Direct Adaptive Steering option, and now I know why.  My new, fully loaded Q50 Premium hash Direct Adaptive Steering and run-flat tires.  After driving it over 1000 miles on mostly highways, I'm deeply troubled by the rather abysmal performance, road handling, and maybe even the real-world safety of this steer-by-wire system.  (As of this writing, I do not know the extent to which the rather miserable run-flat tires may be contributing to this poor performance,  but I suspect it may be quite significant. I will have more to say about these tires shortly.)  For those who may not be familiar with Infiniti's Direct Adaptive Steering ("steer-by-wire"), there isn't a conventional mechanically coupled linkage between the steering wheel and the front end.  Rather, the system relies on an electronic interface between the  steering wheel and the front end.  Thus, unlike conventional steering, there is no instantaneous telegraphing and biomechanical feedback of the sensations that a driver normally feels between one's hands on the steering wheel and the road, particularly lacking the natural progressive resistance that one would normally feel as the steering wheel is turned ever more to the left or to the right.  The lack of this natural  sensation between the drivers hands and the road would be totally unnerving and disorienting.  So, Infiniti has attempted to simulate this sensation by driver selectable settings found within the Infiniti Drive Mode Selector app, found by scrolling through the apps on the touch pad.  After tapping the DMS app, one first selects Steering, after which one has four steering modes between "Effort" and "Response" to choose from, including (1) Light/Casual, (2) Standard/Standard, (3) Standard/Quick, and (4) Heavy/Quick.    Basically, the settings determine the degree of resistance one feels when turning the steering wheel.  With DAS, the  vehicle has an unnerving habit of wandering, floating, and swerving or yawing from side-to-side, requiring nearly constant steering corrections.    Unlike conventional steering, when one is negotiating a curve on a highway with DAS,  you can't simply turn the wheel in and hold it there as you progress through the curve.   If you attempt to do so you will quickly find that a few seconds after you turn the wheel slightly, the vehicle will stop going in the direction of the turn and will begin to go straight, so you have to keep turning the wheel back in the direction of the curve.  This in turn results in the vehicle wandering from side to side. But wait, there's more.  With DAS, the vehicle tends to fall into and follow, for example, any uneven seams or other such things in the road surface. In addition, when one is passing, or being passed by trucks (and even other cars) the wind drafts will blow the car to the side and require  diligence with the steering  wheel because one must anticipate and compensate for this.   I cringe to think how it might perform when driving on the freeway with strong gusting winds and slippery road conditions.  On the bright side, my experience thus far has been that DAS  performs decidedly better when driving around town as well as on country roads.   Quite frankly, I am utterly baffled as to how this steer-by-wire system ever made it into production.  What in the world were they thinking?  It remains to be seen whether or not there will eventually be a Technical Service Bulletin about this glaring problem,  and if so, whether or not a firmware update will even be possible in order to fix the problem.  While driving on highways with the Driver Assist is on, the vehicle will wander/bounce back and forth within its lane if you let it, rather like a bobsled.   In fact, unless you're very diligent about keeping the vehicle on track, the degree of wandering from side to side has me worried that I might get pulled over by the police for driving is if I am intoxicated!  My experience thus far has been that the vehicle wanders the least in the Heavy/Quick setting. As previously mentioned, I remain very suspicious that the run-flat tires may be part of the problem, and  I would be very curious to see how it performs when I eventually replace them with a set of Michelin Primacy tires.   The Internet reveals that the majority of consumers don't like run-flats because they impart a rough ride; they cost a third more than conventional tires; and they wear very quickly.   I find it to be absolutely infuriating that the automotive industry is increasingly cramming these tires down our throats.  Indeed,  I have read reports that BMW for example may void the warranty if these tires are replaced with conventionals. Fortunately, with the 2015 Q50, these tires can be replaced with conventional ones without voiding the warranty.  In addition, the vehicle has a spare tire that can be replaced with a conventional one.