Torchwood spoilers

We learn a lot more about Jack, "particularly his family"

The alien world we see? It's none other than the Boeshane Peninsular (the spelling according to DWM)

We learn more about the history of Torchwood itself

For those worried about Owen's role being reduced, according to RTD the exact opposite seems to be the case - he has "a huge, multi-episode story coming up, which shows Burn at his very best."

There's "some beautifully detailed character work ticking away, in gentle arcs", not just about Owen, but Tosh and Ianto as well. RTD mentions the photo of Owen and Tosh that Tosh keeps on her fridge. He says that "There's plenty more to be discovered about that secret crush". And we all know about the upcoming Jack/Ianto arc.

Gwen's pregnancy? Definitely "alien".

When Martha comes into the team, "she's sort of observing [them] as much as anything else."

Tosh's appearance in the DW episode Aliens of London is referred to somewhere in Series 2.

Burn Gorman - "...in Series Two, you've big changes in Owen. Okay, he still has his foibles and dysfunctions, but it's nice to see him work as part of the team, as a professional. As a medic, as a person, he's much more mature, I think, and more at peace with his place in the team. A lot of episodes are about where Owen's place is in the team, especially with Freema joining - as another medic." Lots of questions are answered about Owen (including why he is like he is)

"You see a huge change in Tosh in Series Two... and that's all I'm saying!" (Naoko Mori)