I've been using a Monkii cage for about three years now, very good product, only possible downside is it's not as easy to drink on the move as a regular bottle cage as fitting the bottle/monkii combination back onto the 'cleats' requires a bit more precision than just shoving a bottle back into a cage. The Monkii cage holds the bottle quite firmly so taking the bottle out of the cage on the move the way you would with a regular bottle cage doesn't really work.
I've also got the larger Gorilla Cage which I used to carry my Thermarest on a lightweight tour in the spring, also a good product.
Good service from Cyclemiles too.