I use Shimano M520 clipless which are double sided without a platform. I find them as easy to use a flat pedals. I find myself clipping in so easily that sometimes I do when I wasn't planning on it.

I test rode a bike with the M324 and found them much harder to clip in than the M520 since the are not double sided and the plaform doesn't give a point target or perhaps the platform prevents the cleat from being guided in if you are not properly aligned. I'm just mentioning this the M324s may look easier to enable a transition to clipless, they actually may make it harder.

Al