I noticed in "Mavericks" windows are not allowed to rest between two displays. If I drag a window between my 27" displays, one half is always transparent, once dropped in place, only half of the window shows based on which display has the largest part. I wondered why, then it occurred to me based on the years of problems with my 24" LED LCD panels and many with the current 27" models. When I set a window between my displays, it was very noticeable that the displays never truly matched, the colors were always noticeably off. This has been an issue with Apple's LED LCD's for years. I wonder if this is intentionally done so people are less likely to notice the matter.