I'm really disappointed with the capacity of the extended battery and especially the price.
You need to do some math. 30% more battery capacity for 25% more cost is an incredible bargain:
Ref :
http://www.dji.com/product/inspire-1/spec
The 5.7 Ah battery has a potential of 22.8 volts, and therefore 129.96 Wh.
The 4.5 Ah battery has a potential of only 22.2 volts, and therefore 99.9 Wh.
Staying on scene for 30% more time to get more shots, regardless of usage pattern, is worth far, far more than 25% more cost. Not just wasted time on the ground swapping out batteries, but the compounded waste of driving to and from the scene.
Compare the following two scenarios, both using 75% of DJI's stated capacities:
Total flight time for 4.5 Ah battery = 13.5 minutes
minus 4 minutes to fly to and from the scene = 9.5 minutes
Total on scene time with 4 batteries = 38 minutes
Total flight time for 5.7 Ah battery = 17.5 minutes
minus 4 minutes to fly to and from the scene = 13.5 minutes
Total on scene time with 3 batteries = 40.5 minutes
Total cost for batteries to give you 38 minutes on scene with 4.5 Ah batteries is $636.
Total cost for batteries to give you 40.5 minutes on scene with 5.7 Ah batteries is $597.
There is simply no value comparison to be made.
Note that the comparison does not even take into account the waste of your time making an additional battery swap.