These shoes are awesome for cracks. I was a little skeptical at first, especially about how much they would actually stretch. They still seem like they run a bit small to me. But they truly did stretch about a size and softened up a lot, making them perfect for jamming into cracks. So far, the flexibility is great.
However, they suck for gym shoes (not sure why the product description suggests that) or any sort of face moves or tiny cracks. The rubber isn't all that fantastic, they're very flexible, and have no edge, making face moves or hard gym climbing rather difficult. The toe box is also wide so I imagine they're pretty difficult in tiny cracks.
But overall, comfortable, seem durable, and excellent in cracks!