Isn't an opposable thumb what separates us from the beasts? I learned the thumb-over F chord before I ever heard the word, barre. It just feels natural to me, and changing to and from C and G7, when playing folk songs in C is very smooth. When I play this chord shape up the neck, I always have a low bass note, on the 6th string, for my alternating bass.I'm a fingerpicker, so I need a free pinky to play melody notes, and the thumb-over technique does that for me. I use my thumb to play an F# (6th str, 2nd fret) in a D chord sometimes, and I play one Merle Travis type, closed C7 chord, in the "The St Louis Tickle". That involves a B7, moved up one fret, with my thumb fretting the 6th and 5th strings, at the third fret. It took a little practice, but it feels natural now.