The New York Times discusses the competition in the frozen yogurt space, with stores like Pinkberry and Red Mango popping up within blocks of each other in Manhattan. The story also highlights Brooklyn's \eks\ (which I have never been to, but now have to go).
After several trips to Pinkberry (come to DUMBO!) I have figured out my favorite combination. It's blueberries or mango, chocolate chips and mochi balls. Yes, it's super expensive but it's totally worth it in my opinion.
I remember when I used to think Tasti-D was the best thing ever, but now I know better. I still love me some Tasti-D, but Pinkberry is my favorite.