What do you want to know?
I've recently plumbed a central heating circuit and hot water pipes with this, on a boat. Previously I used soldered copper in a house, so can compare them.
The main thing with these fitting is to *always* use an insert, and to be absolutely certain that you have pushed the pipe home in the fittings. There is a sort of double-click - one when you push the pipe past the O ring, and another when it is fully home. The H2O fittings are particularly hard to get together.
Speedfit seems durable, and has the advantage of being dismountable.
copper compression fittings will also go onto the plastic, but require room to tighten with spanners.