Shades of Darkness - Discussion

I already have the original Heroes 6 from Steam. I bought it right after its release and was disappointed. I didn't buy any expansions afterwards and eventually stopped playing the game. But now I reinstalled it, and it seems like it's playable now – they've improved it. So, I'm thinking about buying Shades of Darkness, as it has a new faction and so on. But I'm still not sure: those who pre-ordered supposedly get more bonuses compared to those who buy it now. And in general, I'd like to know the opinion of people who have actually started playing.

Added 17 minutes later
Sanctuary, thanks for the link. You know how to persuade. Just tell me, is there a difference in where to buy it? I'm definitely going to buy it on Steam, but I don't know where.