I have been a Linux user since 1991 and understand that things are not always as polished on Linux as on Windows. The Arduino IDE seems to fit this mode. The four cursor control keys, LEFT, RIGHT, UP, DOWN on the number pad do nothing while in the IDE editor. The HOME, END, PGUP, & PGDN keys function as expected. The arrow keys work in the serial terminal and menu functions. The keys work on the Windows version of the IDE (1.5.7).
The plus side is compilation speed. Not that is it "Slow" on Windows, it is about 5 time as fast on Linux (same machine).