Fuel economy needs to be considerered alongside other considerations that could have far greater impact on overall efficiency of flights. ATC shortcuts can save fuel. I am sure high speed descents in A320 can save heaps of gas.
Missing a departure slot could cost hundreds of Kgs of APU fuel waiting for another slot. Being in a position to take a slot missed by another aircraft can save fuel, parking fees etc and can get your aircraft home early to maximise company choices for next operation. If you know company is sweating on this, select a faster level and cost index and hang the extra burn.
A320 taxi fuel flow is similar to cruise rate. If taxi time can be less, however it is arranged, this can save fuel.
How some of these things can be arranged is the subject of a previous autoflight post.
I would like to see pilots comments on a wide angle look at total efficiency rather than simple flight fuel.