I admit that I might not have liked the HZGG 3 cast as much because I loved the old cast, especially AV. However, I feel that I still have a right to judge them based on the old cast, because they are making a sequel of HZGG. If they were making a completely new series, I wouldn't be biased towards them. Because they followed HZGG 1&2, I had my expectations. I know the new actors probably had a pretty hard time, but I can't help my disappointment.
As for actors not getting along on the set, I heard that Zhou Jie and Ruby got along pretty well. On Zhou Jie's websites, he wrote about how he and Ruby collaborated well. I don't know about Fan Bing Bing not liking Vicki, but I did hear once (not necessarily true, since things you hear in media are sometimes questionable) that FBB said if she played Xiao Yan Zi, she could do it better than Vicki. I always got the feeling that Zhou Jie was not as close to the other three main members of the cast, and as of today, he is the least famous. I'm not so sure about Vicki and Ruby being great friends - maybe they really are, but the competition between their fans makes it seem a little less possible.
Finally, the Mainland & Taiwanese thing - it's about the people. If you're really political, it might be a factor, but honestly, I don't think it matters that much.