I bought a 2000 F150 w/ a 4.6. Right now it has a little over 281,000 miles on it. In that time other than routine maintenance not a whole lot wrong. The tranny went at 55,000 miles but that was covered under warranty. I've replaced two coils, and the IAC had to be replaced along with two alternators and a starter solenoid.
At 180,000 I did a major preventive maintenance. I travel a lot and many times its out in the middle of nowhere (80 miles to the nearest garage, forget dealership). So I replaced the water pump, all hoses, the serpentine belt, water pump, thermostat, fuel pump, idler pulley, tensioner, etc. even though there was nothing wrong with them.
So far the valve covers have never been off.
When it came time for me to buy another truck I had a choice, sell the 2000 and get nothing for it (it had 261,000 miles on it), trade it in and get LESS than nothing for it or give it away.
I gave it to my nephew so it's still in the family and I see it every day, it's still running like a top.
I now have an '07 F150 w/ 5.4 3V. So far it appears that I've avoided most of the 3V complaints that everyone else seems to have.
It currently has 96,500 miles on it. I've taken it to the dealer one time so far for a driveablity problem. It only did it twice but it always starts instantly, as soon as you turn the key it would fire up. Twice I went to start it and it had to crank for 10-15 seconds before it would start. Once it started it ran fine. They couldn't find anything wrong (which is what I expected because there were no codes).
It recently developed a couple of driveability problems, an occasional, random miss and an occasional lurch or lunge on acceleration.
With 95K+ I figured I might as well go ahead and take the plunge and change the plugs. At the same time I changed all eight coils. I have been dreading this for months because of all the horror stories I've heard. Long story short, all eight plugs came out without any breaking. Between the new plugs and coils, the miss and lurch are gone and the acceleration is smoother.
For me, on the mod motors...so far, so good.