For me as a frostbite the ideal garment for the winter. Since I have them, I am nowhere cold.
The size I found a little difficult to judge before. I usually wear size 42 and ordered the vest in M/L. I leave the extension zippers on the sides closed and wear the vest over the sweater. So it is still close enough to the body to warm well.
The only downer is that when sitting, a crease forms slightly in the front at the level of the breastbone. This seems to be where the heating elements are located; the fold makes it slightly hot, so you have to smooth out the vest again. Upright sitting posture also helps.
Oh yes, I have two powerbanks that I use alternately. One lasts 3-4 hours on the highest setting. It takes about the same amount of time to charge.
Bottom line, I would buy it again anytime. Gets me through the winter.