I had a 2000 Excursion with a 7.3 for almost 9 years. It had about 182k on it when I sold it and I never had any transmission issues with it. I pulled a 24' enclosed car trailer that weighed about 9500# when loaded and a 27' travel trailer. I didn't find the suspension weak at all and although I had a programmer on the engine, I never towed with it over the bottom two settings. The only weakness is that if the Cam Position Sensor fails, the engine will shut down so it's a good idea to keep a spare one in the glove compartment.
I towed with it in overdrive and never had problems with excessive shifting and felt that it had plenty of power. It didn't have as much pulling power as my 2015 Ram with the Cummins but I also never felt like it was inadequate.
We did have a close call with it when I was pulling a loaded car trailer approaching an intersection when a car cut in front of me and I had to jam on the brakes. The flex section of brake line between the master cylinder and the anti-lock unit blew out and I had an almost total loss of brakes. Thankfully I was able to whip around the minivan that had cut me off and the folks at the intersection saw that I was in trouble and didn't pull out in front of me (the light had turned red). That was the worst experience I ever had with it.
Bill J.
Lexington, KY