For normal Windows GUI use the joystick DOES NOT replace the mouse unless
you use a thrid party app that maps the joystick input into mouse
movement/button presses. You'll find in practice, the mouse is much better
as the joystick is very hard to control to that degree..
For games - it's up to the game if it supports a joystick or not. Many DO
NOT.
Logitechs' Profiler software attempts to overcome some of this but ...