How easy to get and what times do the taxis and buses run from Bangkok airport? How long does it take to get?

through customs? And does anyone know how long it will take to get from the airport to the Citin Pratunam Hotel? And is it a good hotel? Our flight arrives around 11:30 pm. I want to take the bus because it looks cheap but I'm doubting we'll be able to grab our luggage and go through customs/immigration in time since I believe at least one type of bus stops running at midnight but I think there was another I read about. What does customs and immigration entail and is the 'fast track immigration' thing that our hotel offers worth the 1600 baht? They also offer a ride but that's for 1200 baht and I don't think it's worth it unless it's hard to come by a taxi or other transportation.