I happened to take a grab taxi from KLIA 2 weeks ago. 
S70 model. Have to agree the interior feel luxurious but somehow, I get the floating feeling even at 70-80 km/hour.  And I was sitting at the front pax seat.  Both my wife and dotter also feels the same when I asked them later.  So it was not my own feeling as well. 

Secondly, there seems to be a huge vibration coming from the engine when the car was moving from stationary.  It is like the whole front portion shakes/vibrates badly from 0-50 km/hr or thereabouts.  The feel is like your wheel alignment is out and the car wobbles.  It could be also the wheel are not aligned properly etc.  I did not ask or speak to the driver about this as it is not nice to comment negatively to a stranger about his car. 

I made these comments coming from a 3-cylinder SUV Ativa, by comparison.