The service is terrible but the bus itself is ok. I used Royal Express to go from Cascais to Porto in january 2021 and it was difficult to find the place where I had to be exactly. Luckily I found it in time and managed to get to Porto. The bad service started when I had to go back to Cascais and I thought I was in the right place (the general bus station of Porto!!!!) because I saw a Royal Express parked there. 20 minutes before my ride the bus just left without any passengers so I contacted the customer service through WhatsApp and they confirmed (in a not so friendly way) I was in the right place and I just had to wait for the bus because it would be there again at 19:00. At 19:05 it still wasn't there so I tried to contact them again but they ignored me. This made miss the bus and I had to go to a hostel for a night. The next day they reacted by saying they finished their shift so they couldn't reply to me anymore, that it was my responsibility to be in the right place and that they couldn't do anything for me. I asked them in a friendly way to help me book a new ticket because I already missed my flight to the Netherlands because of this. They refused in a very unfriendly way.
So long story short; they don't tell you where you have to be in a good way, their customer service is unreachable at times you need them, they blame you for their mistakes, they are unfriendly and they do not refund anything or help you book a new ticket without making you pay for everything again. I'll choose the public transport train over "Royal" Express any day after this nonsense. At least the public transportation company booked me a new ticket FOR FREE after I missed a train (yeah I know I wasn't having any luck that day).