I think this is a pretty incredible move. I went through Lambda's full-stack program part-time, but I would definitely say it leans more front-end heavy. This will be great for those that really want to focus on the back-end development.
(full disclosure, I was employed at Lambda while going through the part-time program)
As a former student, I can't recommend Lambda. I am speaking to their quality of curriculum and lack of transparency towards their students. I hope from working with Amazon there'll be some quality assurance.