When I drove the D4 on launch day at my local dealer, I was very impressed. I can't really compare against a D2 as it's been a few years since I have been in one (and that was as a passenger), but the D4 made my gorgeous, 98% of extras D3 '8 feel like it was 20 years old.
That said, everyone comments on my car being the nicest they have ever been in, which say's something for the D4 imo.
I will be upgrading when needs be and my D3 has done a million miles to the moon.
I thought it drove superbly, VERY quiet, nice and responsive, less juicy than my D3 and it felt even more huge than mine inside (that was something I noticed alot)
I know they are a little marmite from the back, but they look alot better in the flesh
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07 Silver D3 A/S8L Quattro
S8 front end, Xenons, Bose, Bluetooth, Voice Control, Autodim mirrors, Heated folding mirrors, Double Glazed Windows, Electric Rear & Side Blinds, Black leather Comfort Seats with front memory seats & mirrors, Front & rear heated seats, Interior/Exterior light pack, TV.I.M, AMI, Parking sensors Front & Rear, Air suspension (soon to be lowered), Keyless entry & Start/Stop, 4 zone climate control, Power Boot Open/Close.