For cider vinaigrette: Caramelize sugar in a saucepot. (See tip below.) Once amber, add 2 cups vinegar and reduce by half. Place in a bowl and cool. Add remaining 1/2 cup vinegar. Place in a blender and blend. Slowly add olive oil and season with salt and pepper. Adjust seasoning if needed. Leftover dressing can be refrigerated for later use.
For salad: Place celery, pears and arugula in a large mixing bowl and toss with about 1/4 cup dressing, salt and pepper. Toss gently and taste for seasoning, adding more dressing or salt and pepper as needed. Serve garnished with goat cheese.