I'm not too thrilled by the prospect of a Kate-centric episode
I don't know very many people that are any longer. I lost interest in Kate-centric episodes in Season 2 and lost interest in her character altogether shorty thereafter.
Honestly, her character could die and I wouldn't bat an eye. Juliet or Sun are far more compelling characters now. That being said, it'd be nice if there was at least 1 other strong female character on the show that could take Kate's place. (Though obviously I haven't decieved myself into believing she's going to bite it before - or even likely after - the finale.)
Kate was a really good character in the first season but then fell apart afterwards. What's hurt her is she has become nothing more than the love interest of either Jack or Sawyer. The only other thing she does is go around saying "I have a son!" now. She needs to exist as a character in her own right.
That being said, I gave this episode a strong Above Average. Both storylines, the Oceanic Six and the island storyline were both strong tonight and I love all the time shifting. Very glad to see Jin back and Claire for all of ten seconds. I'm very glad they found a way to bring in Rosseau as well. Evangeline's Lilly cute-as-hell face makes this episode worth is alone.