I can only speak from personal experience, but I absolutely love using a joystick for space. For ground combat I still prefer mouse and keyboard. I have to agree with Tom Paris - you just get a better feel for flying.
It is a bit of a hassle to set up a stick, since it has to be translated into X-box controls first for the game to interpret the input. So you have to fiddle manually to /bind keys.
A small bonus: You can combine multiple buttons for some of your many commands.
One downside is that you cannot use the throttle for throttle. I guess fluid speed control would be a pain for serverside calculations. It can still register as an axis, so it might be used for some nice cinematic camera effects.
I read that camera controls is also trouble if you want to use your joystick hat. I have chosen instead to use the hat for shield boosting, and have a key for looking at my target (PS: I have not tried setting the hat for camera controls, so no guarantees it wont work).
I definately recommmend a stick. But if either of the above limitations annoys you, then save your money.