I have been using the PayLessTax.ie site for a number of years and it is excellent. I also use it to process my sister in laws accounts.
It is very user friendly with built in checks and balances and help and advice and every stage. Before the returns are finalised you are always in personal touch with the team which enables you to build personal and ongoing relationships. You are still able to access your own ROS site at all times. I have no hesitation in recommending the PayLessTax.ie site and I have complete confidence in it.