LOL Andy,
But seriously, I watched an article on these the other day.
They said the problem is everyone knows how to change a tyre but nobody knows how to use these things correctly (myself included).
I think its a generation thing, I could see someone in 20 years time say 'I went to get the repair kit and found a spare wheel god dammit!'
I will always be a fan of a spare wheel but I think if I knew how to use one of those kits i'm sure it would be fine