Wide-angle lenses have three key properties:
1) the wide angle (duh)
2) a very deep depth-of-field
3) distortion of the subjects and horizontal/vertical lines.
Wide angle lenses also have a way of creating distance between the foreground and the background (in contrast to telephoto lenses that compress the distance). Therefore, artistically, you can use the wide angle to create an image where something is in the foreground, possibly distorted, with the background appearing to be very far away, and still sharp.
Due to distortion, having people's faces (or bodies) at the edges of the image is not recommended as they WILL be distorted, and such distortion is rarely flattering.
With a wide angle lenses, placement of the horizon becomes very important. If you tilt the camera down or up even slightly, you'll see vertical lines start to converge, giving you buildings that are falling over...
Used creatively, wide angle views can be very intriguing, but you have to see beyond the "wideness" of the angle of view to really make use of this type of lens.