I can see how this place is popular. Most people come here for the brick/honey toast and crepe cakes, and for the brick/honey toast, you can choose different toppings. You can read all about the crepe cakes and brick/honey toast in pretty much every other review of Is Sweet. Nothing super new or novel on that aspect.
I come here to study since they're open pretty late, the wi-fi is good, and the environment is pretty quiet/peaceful. They have their busy moments when people come in to sit and chit chat with friends over some desserts, but for the most part, it's quiet and intimate. During the day, there's a lot of natural light which is nice for studying/working or the occasional instagram shot.
I usually get hot tea here since it's reasonably priced ($5 for the whole pot). They will also refill your pot with more hot water when you run out which is nice when I'm studying here for a while.
The customer service is good. They're always really nice and inviting when I come here which is a plus.
Overall, it's a nice place to study with decent desserts and cute presentation.