Whisk vinegar and shallot in medium bowl. Gradually whisk in oil. Season dressing to taste with salt and pepper. Place arugula, sliced fennel, and apricots in large bowl. Whisk chopped fennel fronds into dressing. Drizzle dressing over salad and toss to coat evenly. Season to taste with salt and pepper. Transfer salad to large serving bowl. Sprinkle pistachios over and serve.