64k is barely broken in but it's just old enough to be out of factory warranty. Powertrain and emissions warranty will still apply, however you might have difficulty making claims against those. Ford is known to be bit poor in the customer service area (and I can attest to that in my personal experience).
For what it's worth, '04 was the first year of the new body style, so by '06 most of the new model issues should've been worked out. Assuming the truck is clean, no major issues, and the price is right, it should be perfectly fine. I've been looking for an '06 or newer myself.
Also, I was just reading the Lemon-aid book tonight at Chapters and there isn't much good to say about Ford pickups (or any domestic pickup in general). Suffice it to say, there are numerous issues reported with virtually every year of F150. Unfortunately my own '02 is included with an auto transmission failure.