The transmission to which you refer is the 4R100. We have it in our 2005 Excursion mated to a V10. It has been a reliable transmission for our uses towing a 6000# TT, with 125K on the clock. We use the Ex mainly for towing so the 125K has pretty much been heavy duty use, including 3 trips from VA to WY (Yellowstone) up and over the divide and many grades.
Now, we did have a front seal leak around 100K. The seal was only $90 but the labor was $1000+ to drop the transmission. I was told that slow speeds with high temps (say summer stop and go traffic) with a load can overheat the fluid causing this problem. Some folks recommend putting on a larger cooler, but I just decided to stay with the stock cooler.
Other than that issue, no complaints.