Stig79: Except they gave Safana and Jaheira completely new personalities in SoD. Their old personalities are back to normal in BG2. I guess they suffered a few weeks of personality changes during SoD for reasons...
Jaheira's personality in SoD appeared largely unchanged from what I saw. I think Khalid's personality changed a lot more (he's far more assertive and outspoken than he was in BG1. He's still something of an indecisive stutterer, but he actually takes initiative on several occasions). Of course, the fact that Jaheira's voice actress was unavailable when SoD was in development probably means Beamdog had to restrict her role a lot more.
I do agree that Safana's personality changed quite a bit, however. In BG1 she struck me as the kind of "liberated femme fatale" character. In fact, there's actually a line in SoD that I thought encapsulated her personality extremely well: "I do what I want, when I want, with whomever I want." She knows what she likes, what she's good at, and she doesn't care what other people think of her as a result of those actions. I was somewhat disappointed in her romance as a result when she seems to want the same kind of sweet talk and wooing as, say, Aerie.
Of course, you could argue that Safana never really cared for you at all; she was merely using the player as a means of enriching herself before abandoning them when things go sour. Admittedly this DOES sort of fit in with her actions in BG2. I actually found it very surprising when I re-encountered Safana again when I first played BG2 so many years ago that Safana would betray you for some reward, especially if you've been nothing but friendly to her in the first game. I would have pegged that as an action that befits a more Chaotic Evil character, not the Chaotic Neutral Safana's supposed to be. Still, Safana's unexpected about-face in BG2 was Bioware's change, not Beamdog's.
All in all, I suspect that Safana was just a character that nobody knew what they wanted to do with, since she has no real deep stakes in any of the events in the BG games apart from "PROFIT!" I would have preferred it if Beamdog had done SOMETHING to dig more into Safana's past, give us an understanding of how she came to be the person she was in BG1 and how she developed her attitude towards life. Instead I think they focused too much on trying to reconcile events between BG1 and BG2 and ended up not really developing her much as a character as a result.