Regen is worthwhile if your e-bike has a large capacity battery, 3% to 5% regen for a large battery can be up to 6 or 10 miles of travel for a larger battery.
If your e-bike has small capacity battery and short range to begin with, regen braking is likely not worthwhile.
But the interesting thing about the shaft drive is that it can also provide regen from pedaling, similar to a hand-crank generator; charge your cell phone, or other electronics.
I haven't test this e-bike to that capacity, but the bike does have USB outlet for such purpose.
Regenerative Braking on the Electrom LEV
An in-depth explanantion of how regenerative braking works on the Electrom LEV