Terminals and full screen
This is one of the most annoying things I run into while using Linux (which is 90% of the time I spend in front of computer).
When you open a terminal (Konsole, for example) it gives you the default 80x24 size and takes approx. 1/4 of your screen. Type in some long command, longer than a single line. Run it. Ok, now press the UP arrow key to get it back. Everything's fine, the prompt scrolls up by a line, and you see the command, just like you typed it.
Now, maximize the window. Try doing the same. Sometimes, lines just get messed up. You don't see on the screen, what you've seen before - altough it is there. You can edit, run, whetever. What's worse, it doesn't seem to happen for some obvious reason - I tried to find the exact steps to reproduce it, and failed. Still, it occurs on a daily basis, esp. after I've been logged in on remote computer via ssh.