yaar while u have pressed your pedal har there will be no change in acceleration even u change it to the D2 -D3. but on the extreme peak u may get 5- 10 km/hr extra from D2.
for example which i experienced when my car was on D4 and if i press my pedal hard on 45km/hr, it suddenly used to get in 2nd gear (D2) but the maximum speed it goes was about 107-109km/hr but whenever i used to change the lever to D2 from D4 on 45km/hr the acceleration almost seemed to be same but making the lever to D2 it goes to 119km/hr. and same with D3 and while keep pressed on D4. As my car D3 did 155km/hr whereas on D4 it chages to 4th gear on 145km/hr.
this is what i observed.
and yeah my car (City 2000 utomatic) had got 3 points according to the pick i want. but by shifting to either of other 2 points it consumes a bit more of petrol plus i heard someone saying that the mechanic of honda told him that it can damage his car's engine where as i driven mine to 1,20,000 kms but nothing happened.