We recently ate at O Mai with a group of 10 for a friend's birthday. I did not even look at the menu as we chose to eat a family style tasting menu. The food was delicious, from spring rolls and jumbo shrimp rolls to chicken & sweet potatoes in peanut sauce. The evening was capped off with lychee and champagne sorbet served alongside Vietnamese coffee (a treat for anyone who likes very sweet caffeinated items, as it is sweetened with condensed milk).
Our bill was a bit high as we were drinking wine with dinner. The food was reasonably priced for Chelsea and we had a comfortable table in the back by the bar. Service was excellent.