The original version of this tuner, the Peterson StroboClip, was (prior to the release of this updated version) far and away the best clip-on tuner I've ever used. This newer version preserves all the accuracy you've come to know and love from Peterson tuners—one tenth of a cent!—but with an improved screen that you can read in any light level—outdoors, dark stage, you name it.
Plus, it's not just for standard A=440 tunings: It also comes with 50 preset sweetened tunings. I will say that the strategy for tuning with one of these tuners—you essentially have to stop the spinning lights—can take a few minutes to master, but that's more than worth it when you consider how in-tune you'll be. After a few gigs or recording sessions with this, you'll have a hard time going back to cheaper tuners.