I cannot answer that as I do not read the light novel of OreImo, I actually did not know the animated version is apparently a lot less desirable than the one from the source material.
But fortunately this time we have a drama CD of Boku already released so we have a decent sneak preview to make a reasonable assumption of what Yozora's character will be like in the anime. I found the voiced Yozora likeable, although the 'abusive' lines are kept to a minimum in the drama CD scenario but I doubt my opinion of her will change much when it's finally shown on television (maybe I'm a bit biased here since I think Inoue Marina is a good fit). So what I would say is, just try to get ahold of the drama CD and see what you think of it for anyone who's curious.
BTW from what I have seen, Yozora is less of a bitch whenever Rika is involved, because Yozora has zero tolerance for... Rika's interest and she's totally 'out of character' in those moments, if you can call it that.
