I could tell you some stories. The quick version... you know that Alec Peters fellow? Yeah, kind of like that.
I've had experiences with him and he was just one of the most unpleasant people I've met and when his customer base was openly unhappy with the events, he'd just shout them down (I'm a success, you're a punter etc) or ban them. Our local con was a shambles - and he was incredibly rude to anyone who didn't praise his lackluster effort as a godsend. He even went as far to say were were undeserving and 'too cheap' a nation to bother with.
When he banned my wife he refused to tell her what she'd done wrong (she hadn't done anything), gave her some very nasty messages, was very patronising and even threatened that with his magnificent power, she'd never be allowed in London - and no refunds.
Can't say our brief business interaction was much better.
We were considering DSTE as an anniversary trip - but since finding out he was involved, our interest dropped (and we're still probably banned anyway

)