I agree with both of you.
for general web browsing, once you get to a few mbit, the main factor is latency not burst speed. With media heavy sites been an exception.
vod streaming type services is now mainstream, for these 15mbit or so is probably the minimum to comfortably handle these services in high quality. 15mbit on adsl2+ is only for a very small minority.
2mbit to 8mbit on adsl was a configuration change, so someone with a poor line on a fixed 2mbit service stayed with that poor line on adsl max, adsl max was simply uncapping the line.
adsl to vdsl however is a technology change with part of the copper local loop switched to fibre, and in some cases it can be a huge chunk of the line, in my case my copper loop length was reduced to about 300-350m (200m direct) from about 4km (1.65km direct). Ironically I managed to get on the shorter E side this time round with loop length of 2.8km, my area has 2 routes, thats BT openreach for you, I have the short route on vdsl, some poor soul probably stuck on 4km E side on adsl and been told cant be switched.
So in reality in terms of real term speed increases vs marketed speed increases adsl to vdsl should be a massive jump for most people. there also seems to be a marked improvement in stability as well, as those with publicised problems on adsl such as myself, ignition and kwikbreaks have much improved stability on vdsl.