The standard focal length is about the same length as what we can see with our eye. the advantage of this focal length is that there's no distortion or compression, so what you see is what you get. In a way this is pleasing to the eye and gives a very realistic feel to the image. On the other hand, it asks for careful composition and thoughtful framing in order to keep the image interesting. I do the like the sense that it brings of being there, and not feeling like a distant stalker, as with a bit longer focal length, or an absent bystander, which I feel with a wide angle lens. I guess in the end it's all about knowing what you want the image to look like and acting accordingly.
I have worked more with shallow depth of field to bring an extra effect compared with the other focal lengths.
I took the first row of images on the fish market at dusk. Hardly anybody wanted to be in the picture, so I focused on the fish instead, while keeping the people in the back blurry. They were all very happy to see the images of their fish, and I quite like the subtlety of showing the buzz of the market, without having made anybody angry.
The other images were taken on my trip in Paris. I like how with this focal length there is an obvious interaction between place and people.