Not bad, got me onto an earlier coach when I arrived at Dublin airport earlier than planned. I did have to pay for this at time of ticket purchase. No toilets on Belfast->Dublin so go before you go. Facilities aren't great, no covering at Belfast and limited at Dublin airport, so you are going to get wet if you arrive early. (This is Ireland so if it's not raining it's about to rain) Bus is generally clean but the seat pitch is tight and it's not possible to use a laptop if someone is sitting beside you. New operators on this route are significantly cheaper