I realized after the last post that I need to give a real world example. The example that I am going to give is from the recent shot below:
I took this into Photoshop in 16-bit ppRGB and softproofed it to the profile of my local costco's Noritsu and to adobeRGB. In both cases, I show the gamut warning (in grey).
Here is the soft proof for adobeRGB (click for large version):
As you can see a lot is out of gamut in the mountain area that is lit by the rising sun. Especially the green of the trees is far out.
Now take a look at the same for the local costcos:
Far less is out of gamut. Especially the green/yellow of the lit trees is not at all out of gamut, while it was in adobeRGB. This clearly shows that in real world images, you lose colors that even not so wide gamut machines can print if you use adobeRGB as a working space. Of course, there are not really any displays that can actually display these colors...