My friends bought in Primrose back in October, and they've been having issues with mold/dampness, strong odors around their home, and something structural (I think).
KB has been to their home many times since November (when they moved in) to address these issues. KB doesn't have a good reputation, and I personally wouldn't buy from them. I know my friends are fed up and are becoming remorseful buyers.
Even though they aren't in Irvine, I've heard very good things about Shea and Shapell.