Yep, I was there, banging out those command lines all through the early 90s. I ticketed my first online-bought flight through them in 1990.

Pros: FF programs were significantly more generous then, you could book some truly wacky itins and check class of service segment-by-segment, and it was possible in some circumstances up until about 1996 to do throwaway ticketing even for more then just the last segment.

Cons: It took a LOT more time in general to book trips, you'd hit more dead ends if one segment didn't work, and kiosk/online check-in wasn't yet available to allow an avoid-the-humans strategy.

It took years for me to put all the pieces together with segment maximization and the multiplier effect with elite status. My "graduation" was around 1996 in taking a buyout offer so I could travel the world for a year (with FF miles earned making it possible). I had to burn off vacation before my last day (they didn't just pay it; I had to take the days), so I did 3 different LAS trips of 8 total segments RT each, getting upgraded on all the segments.