An excellent ending that I feel nicely pays off all that had been built up in Children of Earth.  I don't have a ton to say beyond that.  It's a well made episode with excellent acting, direction, and writing.  I LOVE the opening with Gwen talking about the Doctor - that might be the best single scene in all of Torchwood, at least in my opinion.

There's a lot to like beyond that, though.  Frobisher's ending makes for a pretty unforgettable experience and left a lasting legacy of Peter Capaldi's acting chops.  It informs a lot of why I was excited to see him eventually become the Doctor after this.  Jack also gets a lot of chances to shine here and really goes through the ringer in this one.  He has a few episodes like this where Jack has to endure some truly traumatic experiences over the course of his time on Earth these last few centuries, but Day Five feels like a particularly tough example of that.  Even losing Ianto kind of pales in comparison to the stuff Jack has to do to his own grandson here to defeat the 456.  It's good stuff, and informs nicely why he takes off at the end of the story.  It feels earned and a natural consequence for everything that has happened these last several episodes.  All this death and tragedy doesn't mean nothing - it is a true death of Torchwood they only barely survive enough to continue forward.