I bought these wellies for my daughter when she was 2, in a kids size 5. The fit has been great, they are comfortable and do not slip on and off when she walks. They are quite short, which is great for comfort although it does mean that her legs get wet when she splashes in puddles. They are made of the typical rubber material, and the soles feature great chunky grips so they are safe and practical.
The main reason why I bought these wellies was the design - there are butterflies and flowers around the boot, and larger butterflies on the front with 3D antennae. This puts them ahead of other similar styles of wellies in my opinion, and adds to their appeal to kids, which cannot be underestimated when you are trying to coax an unwilling toddler to put them on in a hurry!
The wellies have lasted six months and there is plenty of wear left in them, they have simply been outgrown. Therefore I would rate them as very durable. Another advantage is that they are part of a whole range of matching products - you can buy a raincoat, umbrella, hat, scarf etc in the same style.
At their RRP of £17.50 I would say they are overpriced and not good value - they are the same quality as typical high street ones which are generally cheaper than this. If you get them on offer they are a good buy.