A thing I miss in the modern X world: command line arguments
The modern X world of Gnome and KDE and so on has a fair amount to recommend it; applications are sophisticated, genuinely nice to look at, and have a lot of useful functionality. But there are a few things about the old clunky world that I miss, and one of them is command line arguments.
(Anyone who doesn't think that old-style X was a clunky hideous place is invited to start up an old application that dates from those days, if you can find any that are still installed on a modern machine. The Athena widget set was neither particularly attractive nor particularly functional by modern standards.)
In the old days of X, there were standardized arguments (or very close to it) for specifying the application's window geometry (location and size), where its icon would go when it was iconified, and whether it should start iconified or not. In their time I used these both to set up my session when I logged in (a job now theoretically handled by session management protocols) and to start new instances of various applications in standard places, depending on what I wanted to do with them.
These days, well, things are a lot more variable. Some programs have support for controlling some of these things through command line arguments; however, what you can control and how varies a lot from program to program, because much of this stuff is now implemented separately by each program (in the era of old X, most of the command line parsing was handled by the X libraries).
(Yes, I know, GTK has some standard command line option handling. But it's fairly minimal compared to the old X world.)
In theory I can do a lot of this stuff through my window manager. In practice it is quite awkward to have the window manager do this only once, instead of all of the time. (I do not necessarily want all of my terminal windows to start iconic, just some of them.)