On my previous F150, the misfire would only show itself at roughly 45 mph, when right on the edge of needing to downshift to a lower gear or right after shifting in a higher gear. You'd swear it was a transmission problem, but a decent scan showed multiple misfires on one coil. Fix it, and problem solved.
On the Explorer with the V8, it only presented itself under heavy throttle application. Give it an italian tune up, and the misfires would all pop on one cylinder. Replace the coil, and problem solved.
It may seem like if the coil is failing, you should feel it all the time. Reality is it only shows up in certain conditions...