I only play in Insane / Joystick now. Even User-made campaigns.
It takes me, sometimes, an awful number of tries. Retail is not so hard, FS 1 as seen by SF-Junky was a tad (a lot) harder.
I have just finished the ST:R level in which you escort a group of 3 Science Vessels. I also finished PI like this, except I only had a mouse back then, and that I had to lower the difficulty (to hard or average, can't remember) on 2 levels (the one where you must take as much guns as possible on some big thing, and the final one.)