What's amazing is that he had such great results considering his horrific backhand.
I don't think he really had a horrific backhand. It was rock solid, just not pretty. Certainly better than Roddick's backhand for example. Courier's only real problem on the backhand I'd say was that he lacked improvisational feel off that wing and lacked the grace and coordination to storke it effectively when his feet weren't set. Prime Coria (and Arantxa for the women), for example, is about the best I've seen at hitting backhands on the run or open-stance with full steering wheel control.
Courier also could mash his first serve with great direction, and his fitness during his peak was two notches above his closest competitors as well. Also, he was very clutch during his peak as well and other players feared him on important points, because they knew that when the going got tight, Courier kept swinging...if not even harder. Watch the end of the 93 French finals against Bruguera, and with the match on the line, the guy did the exact opposite of Coria. It was like he just grew angrier and more determined and decided to let it out on the ball. It was like he DEMANDED of himself to make big shots on important points.
Also, Courier's variety was underrated. His slice backhand was ugly, but he really knived it and was consistent with it and got a lot of stick on it relative to most slice backhands. He also was a very opportunistic and willing volleyer who knew how to pick his spots and volley off easy winners to conserve energy when necessary or to keep you guessing. He was a rigid, mechanical, buttocks ugly volleyer, definitely, but he was also a highly profficient one.
That was always the thing with Courier's game. He was BY FAR the least graceful technician I've ever seen on a court, yet the bottom-line was that he had a way of making his utter wretchedness translate into just plain effectiveness. Was the weirdest thing and it defied all logic, but the results were always right there for you to see and you didn't know how he did it. I guess you could say his strokes reminded me of wretched poetry, poetry so wretched that it just works...if that makes any sense.