Loved that episode! In general, I don't think every single story should be a "happily ever after," because a lot of mainstream/popular things end happily when that's just not true to life. However, I LOVE Black Mirror and when I watch that show I think, "geez, not every episode needs to end on a grim note." So I loved a different ending to an episode of this show. As a huge TZ fan (a show to which BM is often compared), I appreciated that some of the episodes did have a happy/heartwarming ending.
So while some people say it was too "Americanized" with the happy ending, I thought it was a very enjoyable episode with fantastic performances. And the fact that it was a happy ending for a gay couple makes it a little bit better. (Considering the context of how one of the characters died at a young age, stories like this are still needed.)
Edit to Correct Myself: She didn't die at a young age, but lapsed into a coma at a young age.