I love my Ex. My Excursion, not my ex-wife..haha...anyway...
I have the V-10, it pulls great. My old Dutchmen weighed in at 7k loaded and it pulled steep grades fine. It will rev in the 3-4k range to do it, but thats what its made for and thats where the power is.
Now, you will need to make upgrades to the suspension if the previous owner hadnt. Ford screwed the Excursions up, the made them soft and lower for the SUV Soccer mom crowd. they dont have F250 Springs, they are softer springs, most didnt come with a rear anti sway bar, mine didnt. So I had to add the rear anti sway bar and instead of putting on F250 or F350 springs I put on a Roadmaster Active Suspension in the rear, I left the front alone. It helps tremendously. When I first got it, I towed with out these mods and the rig would be a lane over before I could correct it. Not sway, but drift or wander. The steering boxes are also a weak point as mentioned. I just replaced mine this weekend.
As noted, the gasser is not easy on fuel. I average 9-10 around town and my commutte to work. On the highway at 75, I get 12-14 mpg. Towing....usually 7-8 mpg. You would get better mileage with Diesel, but you need to do the math. HOw much will you be towing, diesel is more expensive per gallon, and higher maintenance costs, 15 qt oil changes will run a couple hundred dollars, plus the extra fuel & water filters and finding someone that can work on them. Those are all things I considered when I went for the V-10.
All in all, I love my truck, it does a great job towing and carrying a bunch of short people & pets along camping.