The whole thing with a child by Starbuck isn't some new plot twist, they've been hinting and laying the foundation for it ever since early 2nd season with the episode "The Farm", and since the first season with the Six in Baltar's head implying that the Cylons wanted such a hybrid. It doesn't just have to be Starbuck, we saw an entire breeding facility, which Starbuck sabotaged on the way out, but it was established that they'd already harvested an ovary from her. That they've produced a child and introduced it to her is new, but this isn't out of nowhere, it's been coming for about a season now.
As for why the cylons want to do it, Boomer explained it quite clearly: "Procreation is one of God's commandments". Bio-Cylons apparently cannot sexually reproduce, they apparently have to be cloned/engineered, but they can reproduce with humans (with a very low fertility rate apparently, from what has been implied so far), so they see mating with humans as a religious imperative.
I see the next episode as being one where a lot of characters get what's coming to them. Baltar may well either end up like Original Series Baltar in a Cylon capitol ship following the fleet or on the Astral Queen as a prisoner (especially amusing since the Astral Queen is now run by Zarek). Definitely be interesting to see how the Colonials treat Lt. Sharon "Boomer" Agathon, now that she's got her prior rank and billet back, and everybody knows who she is. However, it was an interesting choice for Adama to send her, since she's a perfect infiltrator, she can blend in with the Cylon presence seamlessly. I'm also wondering if they will sacrifice Pegasus to let the humans escape.
As for the suicide bombings, I think it's partly that Tigh's plan to disrupt them working, and I think part of it is that they didn't think humans would go to those lengths, and the very concept of it is disturbing to them.
One thing I realized watching this last night, I don't think any sci-fi TV show, certainly none from the US, would have had the backbone to do an episode where the protagonists are suicide bombers. I think back to people who say they watch Galactica because it's the best sci-fi on TV, and since Star Trek lost it's nerve, and I realize Trek would have never had the nerve to do an episode anything like this.