Not three weeks ago I said "Nah, the actor who plays Derek is probably just recording some movie or wanted some time out. Derek and Meredith are the main characters of this entire story, there's no way in hell that they'll kill him or that he'll leave his wife AGAIN and stay in DC" and here we are.
This last Season, this entire Derek vs Meredith fights and relationship issue have been the most annoying thing so far. We had to endure a whole season of Meredith being a "always grumpy, you're doing that again" kinda character, with Derek being a stubborn "this is my calling" character just to have them redeem each other (Meredith is all like "I don't need Derek, but I choose to live with him" and Derek is all "I was wrong, my family is the most important thing, I came back for my family") to just kill him off? That's weak.
After giving it some thought, had to realize that they're setting up for the next few years. This moves Mer into new and interesting territory. A hybrid of her mom, and something else. Those speeches showed a clinical detachment and accepting of situation that could only come from the character they've been chiseling these last few seasons. She's about to become an incredible surgeon and an incredible leader. The entire hospital and direction of the show is about to change.
The whole "I don't need him, but I chose to live with him" and her "streak" make this point really strong. They could probably be totally doing that. However, I still everything I said before is valid: It was a shitty resolution to a 10 year arching story. Which brings us to our next problem:
I think that depends on the type of show. It can work for ensemble shows like Grey's Anatomy and ER. For instance, in the case of ER it means cancelling after season 8 at latest and more likely after 5 when George Clooney leaves. You'd miss the best Robert Romano, Luka Kovac, Abby Lockhart storylines. You'd have no Sam, no Tony.
That is also totally a valid point. The only issue is that this show is not called Seattle Grace. This is Grey's Anatomy. It's really hard to have this story without having Meredith Grey in it. They could have easily moved the Grey/Shepherd family to DC (as apparently both actors are tired of doing this), have Derek working with the president and have them gracefully leave the series. Give the house to his sister, focus on her solving her issues and her relationship with Owen, bring new interns, start over.
The way it is now, we're stuck with Meredith's character, with an actor that probably doesn't want to play the role anymore, with crazy death stories around her, forever expanding family with half sisters and a TV show whose rating is still through the roof.