Probably the best ramen I've had in my life. I had the spicy miso ramen and it was perfect. It had a great balance of flavours. The spice wasn't too overpowering. I can see why it's the most popular ramen at Isshin. The chicken Karaage appetizer was good too but a bit small in portion size. My girlfriend had the Miso ramen (non-spicy) version and it seemed really good too but definitely not as good as the spicy Miso.
We came here on a Thursday night at 8 pm and had to wait around 40 minutes so plan accordingly. Just check Google's peak hours histogram and come during off peak hours (before 7 pm on weekdays).
Service was great. Ambiance was good too. Overall, highly recommended.