Just become proud owner of R350. I got the Aiir suspension package which come with speed sensitive steering. What I feel is over bumps, I got a little effect on steering. Also while driving in comfort mode, steering become too soft, I have noticed it even when comfort mode is off but a little better. Is this some fault? I was driving Audi A6 and it also had the speed sensitive steering, as compared to it, Mercedes steering is not even sensing speed.
I test drove an R350 for the day today and noticed very similar steering performance to what you describe. It seems that the wheel must be turned much further than it should to make the vehicle respond. The car is supposed to replace my wife's navigator, but I am not convinced that it is a better vehicle yet and may wait for the Q7 in June.
In comfort mode, steering is too soft that you can actually feel bumps on your steering. This heppens in all three modes (Auto, Comfort, Sport) but sport mode is more managebale. Auto mode is totally unpredictable, sometime becomes too soft and sometime becomes OK.
I dont know wether I am the only one feeling that or it is the Quality of MB now. I explained it to MB service, they test drive it but said the steering is perfectly ok. Is this the engineering of MB now that they cannot feel the problem.
the worst thing is I got chrysler minivan on rent over the weekend to pick by Plasma, I was amazed that its steering was 100% far far better than my 67K R350. More managebale and more controlable.
Steering become unbearable in comfort mode. 
Linear Mode
