Convertible skates are such a good idea. Snap them to your shoes, pop them off at your destination, no need to carry a pair of civilian shoes with you, no need to sit on a curb or fireplug while you change out of your skates. But why do they always suck?

I owned Metro Blades

Metro Blades, like skating in flip-flops

and Mojos

Mojos, for those who like to go slowly, with poor control.

And I remember other failures. Xsjado used to sell one, for example. And now Cardiff has entered the market. http://www.cardiffskate.com/products/cardiff-skate-s1

The skate has four wheels, arranged in a diamond pattern, which adds to stability but must make turning much harder, and the things look huge, almost certainly harder to carry around than my normal commuting skates.