Are all these icons black-and-white? It seems to be fashionable to use monochrome colors for icons these days (Gmail, many mobile and desktop apps). It makes for a sleek and calm interface. I think its choosing the easy way out. Instead of picking a good pallet and shapes, just remove the colors and all of a sudden a seemingly unrelated set of graphics has something very distinctive in common (it worked particularly well for me in a small newspaper where low quality photos were contributed by different authors, just make them grayscale, voila).
Really, color is such a great way to convey information.
These are for use in menus, submenus, notification areas, toolbars and the like. Locations where you'll be presented with a few choices that are easily distinguishable. They're not designed to be app icons. They're designed not to distract away from the rest of the app, especially the content.
Really, color is such a great way to convey information.