Can't speak for GTI but on my GTD it works much better on my new car but it did on my old car.
On the old car (GTD) there was a noticeable difference between eco and normal driving mode with the eco being a lot duller and devoid of any feel and to be honest not really much more (if any) economical.
On the brand new GTD however I'm wondering if VW have been listening and have tweaked the map for Eco, as it's much more driveable now without that horrible dead feel from before. Add to that, it really does add to your fuel economy now (at least it does in mine), by a good 4-5mpg