You are right Paul, in my opinion they have two things that let them down. One is the push down terminals as you mentioned, but once you get the hang of them it is easy, there is a particular angle that they go in at and when you get it it is much easier.
The only other gripe is how the terminals are laid out - they are live, neutral, live, neutral, earth earth. If they had the earth between the live and neutral they would be a lot quicker to install!!