Bastila...she's always been an enigma to me. On the surface she's your stereotypical ***-kicking heroine who happens to be a Jedi. Plus given that I do not view the Jedi Order (not including the New Jedi Order) favorably, she did not have much credit with me to start with.
Then I started listening to her dialog carefully. Her personality is interesting: her personal demons are mostly self-perpetuated, but are also fueled by the foolish Jedi ideology of stifling one's passions. You actually feel sorry for her.
But then she gets turned to the "Dark Side." That isn't the "Dark Side" (provided that the Dark Side actually exists), that's just the Bastila Annoyance Enhancement Mod that Bioware not only threw in but actually hardwired into the game. Actually, it's not entirely Bastila, it's also characters like Malak and Atris: they all instantly regret their actions when they've been defeated or are about to die. No one just flips convictions like that. Plus her dialog at that point is so...wooden.
On the other hand she actually pretty hot in that Dark Jedi Robe.
In terms of game play, I wish she was more powerful, especially as a Sith. She's the second least powerful member of the Party (Carth being the worst). I wish she had some unique powers (maybe actual Battle Meditation).
Those are my thoughts.
Oh, and Visas is one of my top TSL faves. And yes, she is quite the looker.