I've never been to this place's physical premises, but I used its website to order flowers for my friend's birthday. They have an enormous selection online for all sorts of occasions. The morning of her birthday, I got a very apologetic phone call from the florist explaning that they didn't have any of the flower I'd chosen that day. I explained the circumstances (friend's birthday, what her tastes were like) down the phone, and told them I didn't know anything about flowers so I would leave it up to them to choose a replacement arrangement. A few hours later, I got an ecstatic email from the friend -- they had chosen an absolutely beautiful arrangement of mixed flowers, perfect for her tastes, and she was over the moon. So, thank you Grecian Gardens!
Pros: good website, great customer service
Cons: quite expensive (though maybe not for manhattan!)