Yes, it's called motion burr.

Propping an SLR firmly against one's head, with one hand on the side/shutter, the other under the lens, and both elbows tucked in and pressed firmly against the chest.. gives fantastic stability. This allows slower shutter speeds and lower ISO settings, yielding better depth of field control and higher quality photos.

No real difference for tourist snaps, which make up the bulk of my "photography", but quite a significant difference on the snaps I want to blow up and print LARGE.

Mind you.. the proliferation of optical image stabilization is helping us tourists get a lot better quality images despite our poor camera holding technique. Combine the two, though, and the photos can really pop!

Cheers