I've used Digital Color Meter and an "app-ized" version of the default OS X ColorPicker, among others, but this is what I've been looking for. Call me crazy, but I like menu apps -- one less thing to have to find and launch when I need it, so they fit well into my workflow, regardless of which app I happen to be using now.
The price is fair, too -- $5 is less than the cost of a sandwich, and something tells me I'll get plenty of use out of it. Tested and bought. (And on impulse, I also picked up the company's other app, Snippet, which may finally wean me away from using Stickies).