Place potatoes in large bowl. Generously spray potatoes with nonstick spray. Toss to coat.
Sprinkle with 3 tablespoons thyme and garlic salt. Toss to coat. Spray large rimmed baking sheet with nonstick spray. Arrange potatoes, cut side down, on sheet. Roast potatoes until tender and golden brown, turning every 15 minutes and roasting about 45 minutes total.
Meanwhile, stir vinegar and sugar in heavy small saucepan over high heat until sugar dissolves. Boil until liquid is reduced to 2/3 cup, about 10 minutes.
Mix in remaining 1 tablespoon thyme.
Transfer potatoes to plates.
Drizzle some balsamic syrup over potatoes.
Per serving: calories, 208; total fat, 1 g; saturated fat, 0.5 g; cholesterol,
