I'm 5 11 and a 1/2 (or at least was, don't know if I've shrunk since I was last measured) - I'm not 6' - that would be a fib, I'm 1/2" shy. I drive with the seat about 2/3rs way back, with the seat back quite upright and the steering wheel at its highest point.
I find the driving position great, and the high seat contributes to that. When I get in 'regular cars' it feels wrong! To slouchy and like the car wasn't built for people to sit in comfortably.
I have zero problem with headroom - in fact there's a good couple of inches to spare above my barnet. The view out of the windscreen is fine.
If I swing the sun visor straight down it definitely does obscure far to much vision - it extends well below the bottom of the rear view mirror and only leaves a small gap above the steering wheel which is basically a view of the bonnet and not much else. For my Mrs, who's much shorter, that view might be fine though. If push the sun visor right forward so it turns up and is touching the windscreen, the view is fine and it does its job - I may need to bring it back down a bit if the sun is very low in the sky.
I would have thought that if you have trouble with head room or the sun visor in a Freelander, you'll have trouble in most other cars.