I'm an unabashed meat eater, and Hache is my sort of place.
The burgers are excellent, cooked to your specification. They're are juicy and tasty, and the toppings are always the right side of generous. You don't get absurd GBK style burger towers; even the most generaously proportioned burger is pick-upable and doesn't need to be deconstructed and eaten in picees. I always go for beef, but friends have had duck and tuna, and I almost got food envy as I dipped into my bovine delight. They are right, this is the best burger I've eaten in London by quite some distance!
I've never had starters or desserts, but the sides are generous and well cooked.
Milkshakes are great, but you really need 2 to last the whole meal – a large size would be really handy.
Service is friendly, and though sometimes it takes a bit of effort to get your order right with the staff whose english is less than conversational, however their willingness to try is good, and I've never had to send anything back as wrong.
The atmosphere is great, it manages to be cosy and intimate when you're there as a couple, and open and friendly when there's a group. How it manages to do that I don't know, but well done Hache.