I have had mine for over a year and 18000 miles. It is very stable at high speeds. 136mph and it does not even twitch. 18" tyres and 2 wheel drive so the quatro should be even better.

Want to elaborate as to why? You got me curious.

That's encouraging. I just took delivery of my A7 and I love it. It is so much smoother and quieter than the XJR VDP SC it replaced I have to be really careful not to be significantly over the speed limit. Based on its performance at 90 mph I wouldn't anticipate any issues at higher speeds. I have 19" AS and they handle brilliantly.

My 1 year old A7 TDI Q 245 S-line is a firm but sure-footed ride. Quite a bit MORE stable @140 than my S6 was... As borodin says time moves on. I like it, appears to send more torque to the front than the S6 did making it run slightly wide in the tight bends compared to the S6. But fast stable motorway cruiser so am a V happy bunny. Achieves as much as S6 & q effortless.