It's the same, everything is just a little bit different.

The language is clunky, because we have no real-world counterpart for what we see. We see two realities, side by side, each of them mutually exclusive, and we have no idea if one is more viable, more real, than the other, so we can't really say one is alternate. We've seen flash-forwards, and flash-backs, but what do we call this? How can we describe the relationship between the two? Well, a minor war broke out last week over there at Lostpedia; they're fighting over terminology instead of discussing their views of the story itself. As a life-long fanboy, first Star Wars, then Star Trek, and now any number of things, this quibbling over minutiae really pisses me off, because they're missing the point: it's the story, stupid! Sure, flash-sideways is an awful, awkward term, but it's what we've got. Deal with it.

Moving on, I just read an interview with D&C in which they discuss the parallel timeline and its differences to what we know. Yes there are differences, but it's not really crucial to our understanding to catalog them all and try to find out exactly where the timeline split. That being said, D&C want to bring our attention to all the things our people didn't think about as consequences to their action, like the Island being underwater. I won't tell you the whole thing, just read it for yourself. Also, check out this video from comic-con: a segment of America's Most Wanted, featuring our very own parallel Kate:

Also, I got my hands on something that I do not consider a spoiler, but some of you might: the names of the upcoming 3 episodes. I'll post them here and now, but in black text so you have to highlight them if you want to read: The Substitute, Lighthouse, and Sundown. That's all the info I have, and I wouldn't post anything more even if I did. I hate spoilers.