Have had issues with noise. Mainly caused by the type of expansion vessel they were shipping them with.
I understand they are now using a different type of vessel with a non restricted opening to the vessel.
They sent me one free of charge to an installation I had issues with (as part of their trial) and it solved the problem.
Other than this, I've no major complaints. I do find the posistions on the flow and return and the cold feed a bit odd. In this day and age, we could site them over each other and not off set round the cylinder. Just means its more work to make the pipe work look neat. But then they arent the only manufacturer guilty of this.