The erosion of middle-button paste functionality is a continual frustration.
There are cultural differences between the Windows and Macintosh personal computing worlds, and that of X11 on Unix workstations. While always allowing customisability, we should hold on to the good ideas of the past, rather than dismiss them as being unfamiliar to the personal computer user.
What irks me especially is that the same forces that are driving us towards a Windows-like experience on the Linux desktop are also removing the ability to easily customise our environment, if only to retain the functionality that is being deprecated or dismissed. (I'm looking at you, GNOME.)