Had to climb most of the Heathfield TV transmitter mast once, was flippin' freezing, wet and could feel it swaying about in the wind. Definitely focused the mind on not missing my footing or forgetting to clip onto the safety line. But nice views out to sea, planes heading into Gatwick, Canary Wharf etc.
Not quite on the same scale but seem to recall some knob climbing the floodlight pylon in the NE corner at The Goldstone. Kept the crowd amused until he was persuaded to come down.
Probably vomit myself to death in the lift on the way up; but I'm OK-ish with really high heights where its obvious you'd definitely die rather than be horribly maimed by a fall.
I did the edge walk in October 2011. First time to Toronto, first time up the tower, so i thought i'd do it properly.
It's actually pretty good, the people who run it were quite amusing and you get the usual photos and DVD etc.
One plus is you get to go up the tower normally as well, so did the edge walk before dark, had some food and beers then went up to the usual observation area to see Toronto by night.