Finally downloaded and finished the campaign. Spoilers, probably, but if you've read this far into the thread you should've downloaded it already.
Didn't have any crashes, although the campaign was extremely slow and graphics intensive. Mostly my computer's fault, not yours. The only way I could get a good framerate was to play 640X480 with those FPS-killing nebulas turned off.
It's hard to say what the best campaign of them all is. But I get the feeling that PI is the best one I've ever played. Extremely difficult, but I liked it even though I had to cheat on practically every mission. Great music selection. The biggest weakpoint is probably the last mission, where I found myself in the proverbial "killing an aircraft carrier with and ML-16" situation.
Also, my computer is crap, but somehow I played the campaignt through without any memorable CTD.