Thanks for all the feedback and suggestions about improving Photoshop’s color-picking tools. I’ll reply to many of the comments once I get a few free cycles.
In the meantime, I notice that many people are asking for Photoshop to gain the ability to sample colors from outside the application. That capability is there already: grab the Eyedropper Tool, then simply click and hold on a document, then drag elsewhere on the screen. Notice that the foreground color on the toolbar keeps updating as you move your mouse. When you let go, the sampled color will be your foreground color (or background color, if you were holding Opt/Alt when you clicked). I’ve confirmed that this behavior works on the Mac, and I believe it’s the same on Windows, but I don’t have a machine handy on which to check.
Clearly this behavior isn’t very discoverable, but I’m not sure what would make it easier to find. Some commenters noted that the color picker in Flash and other former Macromedia apps makes it easier to sample colors from outside the app: when you mouse away from the preset color swatches, it keeps sampling colors under the mouse. That’s true, though I’ve often found that behavior annoying (i.e. I end up sampling things I didn’t intend to sample).
I’m glad the topic has come up, and I’ll bounce some ideas around with the UI and engineering folks. Hopefully there’s a way to get the best of both worlds.