I've used Flickr once or twice before. The wallpaper on my computer right now is a photo from Flickr. I found it easy to use. Picasa was easy to navigate as well. I'm not too interested in people photos. I like quirky landscapes, animals, art, and maybe babies if they are uber cute or whimsical.
I like this one because it reveals an unusual landscape for Hawaii; A view you might not normally expect to see. Yes, I think that is a horse in the picture. Ah...just a country girl at heart.
This tags were simply 5, 6, day and Hawaii.
My 2 (technology) cents.