Last season, Lost really hit its stride. Despite the strike-shortened season, the producers and writers seemed confidently in charge of the story, and they didn't waste a single episode like they have in the past (I'm looking at you, Nikki and Paulo). And the show hit its emotional peak as well with the Desmond and Penny romance, particularly in "The Constant" and the season finale.
With the flash-forwards becoming a staple, Season 4 also revealed the six survivors who got to leave the island. They are: Jack (Matthew Fox), Kate (Evangeline Lily), Hurley (Jorge Garcia), Sun (Yunjin Kim), Sayid (Naveen Andrews) and baby Aaron.
The trailer is still up here:
http://spoilerslost.blogspot.com/2008/10/first-real-promo-for-season-5.html
And it's awesome.