gzt: Manual cars used to engine brake at the lights etc all the time. Regen braking is no different. Just an intervening 25+ years of predominant automatic transmissions : )
I'm always looking 12 seconds up the road as I was taught, so if I can see the road ahead is clear, but need to slow down due to traffic immediately in front of me, I typically won't use the brakes. This avoids the needless chain reaction where successive people apply their brakes harder than the vehicle in front, until eventually everyone comes to a complete stop. On the other hand, if there is slow traffic in front of me that will slow everyone down, I will use the brakes so the vehicles behind me can close the gap earlier than needed, in case they aren't paying attention to the road ahead. I'd rather they be close behind with relatively less potential energy.