The standard ride in the non-ACC equipped car is fine. My MK7 GTI feels similar to my old MK6 GTD (but much better on the bends than that car was) and it is definitely smoother than my old MKV GTI. The improved interior quality (less noise, etc) might have a lot to do with that though.
If you've owned a MKV/VI and/or you are used to large alloy / firm suspension setups, then you have nothing to worry about. In fact I really dislike soft suspension, so I've no doubt that if I did spec ACC I'd always have it in Sport / Normal mode, therefore for me it would be a total waste of money IMO.