I have an ES on order and have had a three hour test drive. So, not much Lexus driving experience BUT I have driven 500,000 miles in BMW 4 cylinder diesels and 90,000 miles in the E class with the new 4 cylinder diesel.
These have all been great cars but when starting up and at slow speeds/around town/heavy traffic the Lexus is without question both quieter and smoother. At speed there is little difference.
Sure, the Lexus won't handle.as fluently but if you need to drive 200-300 miles a day it is less important.
The BIK tax saving is significant too!