It's hype, that's it.
Doing some "informal" testing with a volt meter, and a penny dropped from 6 inches exactly (to ensure the string was struck with the same force every time), using the same guitar, I tried both an F-spaced Evo and a non-F-spaced Evo and found the output on the "misaligned" strings to be identical. (Well, the averages were identical . . . the voltage is very small and drops off pretty quickly, so 10 drops averaged on each gave me . . . um . . . damn this memory of mine . . . the same numbers, yeah, that's it. ;-) )
Keep in mind, not a controlled experiment, but it was more than enough to convince me that what my ears are hearing is correct, electrically there really is no differance.
Plus all my local stores charge a little more for the F-spaced, so I don't bother, I'm Po' enough as it is. :-(
Oh, the F-spaced pups do LOOK cleaner, with the poles all nice and lined up with the strings . . . so that's really about it. ;-)