I've been stalking this shoe for a year. Last year I bought wedges and this year was flat/sandals. I read all reviews on this shoe and took everything into advisement.
I slipped my wide foot into the left sandal and it felt like ecstasy. I took my time to make sure the soft lip barrier between the zipper and my heel was soothe. Make sure you scooch your foot forward a little to give room for the zipper to caress your heel.
Yes, they are slippery especially if you tend to step using your toes. I shifted to rolling off the balls of my foot which remedied the slippery situation. I've gotten loads of compliments.
Now I'm hunting down their previous models in red. These feel smooth like butter and I look forward to collecting all colors.