+1 to having a front brake. In addition to the issue of total stopping power, coaster brakes have some weird failure modes that I've experienced over years of use.
If your feet leave the pedals for any reason... no brakes.
If they're in the wrong position when you need to stop... greatly reduced braking power.
If you're on a steep descent, greatly reduced braking power
Been there with all of those, and I'm an experienced urban cyclist. Some failures can be prevented by perfect attentiveness and anticipation... that's not good enough for me. It's tempting to omit the front brake because a stripped-down bike is simple and looks cool, but routing a front brake cable really doesn't add much in the way of complexity.