The Crystal pumps have their own story to tell. Due to the see-through nature of the Crystal pumps, high heel feet may look better depending on your preference - however, both default and high heel feet will look like they are floating inside the shoe.
Depending on the position of the foot inside the shoe, you may see a dark patch/shadow on the side of the foot - this is just the vinyl clinging to the foot. If you find the shoe difficult to get on then just heat it up with either a hairdryer or run it under hot water without burning yourself.
Air bubbles and dust in particular stand out due to the transparency of the Crystal version. The air bubbles actually do look good if you are lucky to get some because they look like champagne bubbles.
Crystal pumps may appear to have a slight yellow tint or develop one over time.