I'm not sure what I like more at Guu - the food or the energy. Both are incredible every time I've been there.
I'll start with the service. Part of the fun of going to Guu is having 20 employees yell at you in Japanese when you enter the restaurant. They're yelling because they're happy to see you! The key is to embrace this and roll with it. It's a lot more fun if you interact with the staff. The servers are always really busy, but I've never had an issue with waiting for food or assistance.
The food is amazing. Some days all I can think about is their salmon tataki (my boyfriend and I each have to order our own because it's too good to share). Other favourites include the udon and the kimchi hot pot. Deep fried brie is also an item we usually order (it's hard to pass up deep fried cheese).
Overall, I'd recommend this place to anyone that's looking for a place to have a good time at (it's pretty popular with the drinking crowd it seems, although I typically just go for dinner). I also think it's a great date spot if you don't mind going to a place that gets a bit loud.