Hi Kremmen
About ECON it hass effect on climate controll - in hot day if you using climate control without ECON the climate control can blow air with high speed, but when you press ECON button theclimate control air blower speed reduces and cabin temperature not keeping always same temperature that you choise but can rise if you cooling cabing and recirculation for air choisen (the speed near knob may remain same but you can hear that speed of blower reduced)
About acceleration with ECON pressed - if i gentle on accelerator pedal and i pushing ECON i can feel little reduction in power (lets say it`s like if you drive an old car with 1.0l naturaly aspirated engine uphill and when acelerating hitting air con on)
About regen braking without ECON - its more powerfull from my observation, when i removing my foot from accelerator and when pressing braking pedal .
This make sense because bigger economy is not when regen braking used but when car glades (no aceleration and no braking used) that reason to use ECON and B mode in town, when you gentle on accelerator you can catch its position where regen is almost not applied, you can check this when you driving downhill but becarefull when you in B mode and releasing accelerator fully you speed redusing fast like you pressing brak pedal but stop light not activated !!!
But if you doing small trips without A/C (lets say 6-8km) in town with speed up to 40km/h and gentle with accelerator, allowing to car reduce speed slowly without hard regen braking if you need to stop you can get same fuel economy as with ECON pressed.
About fuel economy when my Jazz new it suffered firs 2 month from brak pads dragg. The pads was new and i almost not used them, several times i heared noise from rear of car when started to move (noise like from heavy car that braking hard but there was no car near me) I let to honda service check car -they told me that they not found something wrong with braking system but after this check that wooping noise from rear of car not came back and fuel economy started to rise .