Puppy Face , Jul 07, 2006; 10:32 p.m.
Shoot a few RAW files and open them in DDP. Cycle through the Pictures Styles and decide for yourself. The differences are somewhat like using different films, e.g., Velvia vs. Portra 160. So there are differences in contrast, saturation and color tint (warmer/cooler).
If you shoot RAW, the selected Pictures Style will open in DPP as the default. However you can change the style or other parameters to your heart's content prior to conversion to TIFF. The style is merely a tag and the RAW file is untouched. The main idea is to find a style nearest to your taste and therefore save time postprocessing. My fav Pic Style is landscape and I often find it very near to the look I want. It makes sense as I mainly shoot landscapes. However once in a while standard or portrait look better.
Incidentally, some non-Canon RAW converters don't recognize Pictures Style tags.