I ride with mine exclusively in stop and go traffic.

So its definitely a little more annoying thats straight up platforms, since there is a right side up... But, its MUCH easier than toe clips.

I found when the powergrips are new, its kind of annoying and I often just rode with one foot in, and the other foot on the platform side, until I cleared an intersection and had a moment to flip the pedal.

BUT,

as the powergrips wear, they tended to fit the form of my foot better and better, and often times i start pedalling, and found my foot naturally found its way into the powergrips accidently and naturally. After a few days of breaking in my feet almost always find their way naturally into the power grips as I get started, and only sometimes do I have to think about flipping the pedal up first.