I've tried the tutorial levels with both mouse+keyboard and joystick+keyboard.
Both are perfectly playable and I had fun with both, though personally I did find the joystick much more intuitive -- with the mouse you do sometimes have to scrub it across the mousepad a bit to do sustained turns, though I guess you would use the keyboard for that. I can see why a trackball might be preferable to a mouse.
I must say I found speed control easier with my joystick's rudder than with mouse+keyboard plus it meant fewer key bindings to memorise. In fact, in general, the joystick means many fewer key bindings to memorise. Maneuvers such as corkscrews, pull-ups and crazy Ivans were also, for me, much more intuitive with the joystick, but I'm sure with practice I could nail them with the keyboard, as I did for X3.
On the other hand, I found precise targeting easier with the mouse than the joystick.
BTW It's worth noting that you have to explicitly enable mouse support in the options: it's off by default and that confused me the first time around.
Hope this helps!
Edit: if you do get a joystick, I'd advise getting one with a twist stick such as the Logitech Extreme 3D Pro. By setting the twist to control roll, you can do corkscrews etc with just the joystick, freeing the other hand for targeting, power management, etc.
Post edited October 06, 2008 by sailmaker