We went on Wednesday and everything was very quick and easy. I was concerned there'd be a lot more security after the Paris bombings.
I just wanted to update that there is a passport photo booth for US sized photos for £7 in the lobby of the Visa section of the embassy.
I printed pictures from the website that was given to me in this thread, but just in case, I wanted to let people know that there is a photo booth at the embassy!
They have a really nice children's play area with soft structures, books, and they show CBeebies on the TV. They also now allow smart phones and iPads in, as well, so the kids are well occupied.