I have had my 2000 7.3 4x4 for just over five and half years now. I can’t really speak to other years/engines/models, but here is what I know:
When you are doing an oil change get used to thinking in gallons instead of quarts. I buy four gallons and will use 3 and about half of the last. I use Rotella T-6 full synthetic, which is nice because I also put it in my BMW and motorcycles when I had them. I use Motorcraft 1995 filters which you can find pretty easy at most auto parts places, I think Walmart might have carried them too. It’s nice that you don’t have to use a jack, ramps or anything to change the oil.
I replace fuel filters every 15k or so, they are easy to do since they are right on top of the engine. I get a bunch cheap online. I run B100 in the summer and at least B20 in the winter; I don’t think it really matters, the old filters I take out never look all that bad.
4X4 Excursions have solid axle leaf spring front ends. It doesn’t ride like a Suburban, it rides like a truck. Also, if you look closely you will see that the springs are just an inch or so from the bump stops. Ford forced de-arched springs on Excursions so that soccer moms could fit them in their McMansion garages. Supposedly swapping to same model-year F250 springs gives you more travel and a better ride. I haven’t done this yet on mine.
Excursions also go through ball joints pretty regularly. When you replace them use good parts that are greasable and grease them. I also had to do front wheel bearings, not a hard job and again use good name-brand parts.
Sway bar end links are a crappy design and will wear out causing a clunk in the front end. Your options are to either remove the bushing material from the original links and replace with poly, or replace the whole link with a ball-jointed MOOG “problem solver.” Or I suppose you could replace with OEM style and just plan on re-doing it every 25k miles.
The water outlet/thermostat housing is a crappy stamped metal design that will leak eventually. Just plan on replacing the housing whenever you flush your coolant, it’s available cheaply aftermarket. There are also reinforcing rings and even billet aluminum housings if this really becomes a problem. On the topic of cooling systems, be sure to use a coolant or coolant additive to prevent cavitation. Not that much of an issue on Powerstrokes, but worth spending a few extra bucks to be safe. Oh, and replace your cap with an aftermarket one – the OE one is a crappy design and probably isn’t holding the pressure it was designed to hold.
Power lock actuators are an issue with all Superduties, I just replaced the bad ones with Dorman replacements when we first got the truck and haven’t had any problems since.
That’s about it. Other than the above, five plus years of ownership and no major problems. Seeing as there is really nothing out there to replace it, we plan on keeping ours indefinitely.