Weird, I was thinking about the exact same thing the other day - as I was driving over the Queen Elizabeth II bridge (at Dartford, see:
Dartford Bridge) and espied some the bridge's maintenance team going about their work right at the very top of one of the upright pylons (137 meters, or in 'old money', 450 feet above the Thames)
I remember looking up at them and feeling almost nauseous with vertigo - and yet one hour before I'd been up in the FL300+'s - as Claret says, it's different (sort of).