Blur does exactly what it should do in an easy way - create blurred versions of existing images on your phone that you can save as your wallpaper.
It's one tap to upload a photo, one to crop (slightly annoying that you always have to do this) and a sliding scale to blur the image or change the color scheme. Then it's a short tap to save to your image library or press and hold to set as wallpaper.
Overall, Blur is simple and works well, while the wallpapers look good. What more do you need?