Unless you've used a pure wide-angle lens it's hard to appreciate the differences, there's less of the exaggerated pulling effects at the edges of a similar SLR lens, it's less distorted.

I use the equivalent of a 21mm Leica lens on my 5x4 camera and in most of the images you wouldn't realise how wide angle a lens I'd used. In the early 1990's I used a 21mm on my Leica for a few months and was extremely impressed with the lens.