I bought a 12-oz Tall for $4.25.
Given that chestnut is a fairly mellow flavor, this ended up tasting a lot like a caramel coffee drink but not as buttery. There's not much in the way of spice or chestnut other than a vague hint that was similar to toffee nut.
Beyond that, the drink is very sweet. The spiced praline crumbs add a candied crunch whenever you come across them.
Nutritional Info - Starbucks Chestnut Praline Frappuccino - Tall (12 fl oz)
Calories - 290 (from Fat - 100)
Fat - 11g (Saturated Fat - 6g)
Sodium - 170mg
Carbs - 46g (Sugar - 44g)
Protein - 3g
Caffeine - 70mg