I bought into the hype! I was there at like 10AM to get mine (and one for my husband).
After some hesitation, I tried it and I really enjoyed it! It started out sort of like a dreamsicle - a mangoy dreamsicle. Then came the tart tart tart. It was really quite delicious! The sprinkles type topping was exceptionally tart. When I asked my husband he said "the pink syrup is mango, the pink powder is apple, cherry, radish, and sweet potato. The blue syrup is white chocolate mocha and the blue powder is sour."
Sadly, I feel Starbucks under-estimated the draw of the Unicorn Frapp, because my local Starbucks was sold out by the next day. I hope they bring it back. It was totally worth the splurge of sweetness. I was also disappointed that I went back the next day and they were out, because my daughter was really excited to have one and not ever did I think the drinks wouldn't make it to day 2. Ceste la vie.