Thanks for your reply, Kevin.
A couple of service managers I've spoken to mentioned that getting service under some aftermarket policies can be a pain. I've heard nothing either way about 1Source (as yet).
I've tried to email some folks about 1Source but they've not gotten back to me with their experiences or those of their friends/colleagues.
The service manager at the Ford dealership where I'm purchasing my Explorer told me that they've had good luck in the past with GEICO's MBI as an alternative to a Ford plan.
The good thing about GEICO's MBI is that it's "pay as you go", roughly $40 some odd bucks for every six month period with no outlay of money up front. So you can discontinue the policy at any time and only be out the money you've paid for coverage to date. (You must elect it within 11 months/11,000 miles on a GEICO insured vehicle.)
The coverage extends to 7years/100,000 miles.
The bad thing is that you pay a $250 deductible for any covered work. If you have several repairs, obviously that would run into some money.
Still, your out of pocket (barring repairs) would be under $600 for the 7 year period, and you'd have protection for major work where necessary.
I'd still love to find out if 1Source is a good/reliable company. I see that they're listed with the BBB in Colorado but I'm not sure that that's reason enough to take the plunge.
Hope to hear with others that have experience, good or bad.