I tasted 10 dishes and liked 8.5; some of them, I liked immoderately. It’s a homely, fun casual restaurant, suitable for friends’ gatherings, after-work, or just a fiesta. It’s worth visiting at least once, more times if you go with different groups of friends.
I've never been to Gaggan in Bangkok, but I was able to get seats at his casual offshoot down here tonight (43 Craig Road, 9654-4351).
Some hits and misses on the menu for me and generally, the more Indian-centric dishes like the curry and biryani fared better for me than the Mexican-inspired elements like the tacos. There is much hype about the Gaggan brand and if this is one restaurant you are curious to try regardless, manage your expectations.