In the departure terminal there are a few shops, Starbucks…Inside The Body Shop, Coffe beans, souvenir shops.
Have in consideration that traveling by boat in monsoon season is not advisable at all and the poor conditions of the Borneo Highway (together with the broken old buses), it is much recommended to flight, especially Air Asia offering good deals(even last minute deals are quite affordable for western, around 150RM for following day from Miri to Kuching)
Unfortunately, Wifi is not available on the airport, unless you go to any of the major coffee shops brands. Also, there is no refilling water station. Once flying to Singapore I suffered a severe delay of 2 hours with Tiger Airlines. The ground staff was quite accommodating, giving us updates regularly. As last option, We were given our checked baggage to carry on the flight, seated in the first row and apparently informed the ground staff in Singapore. We had 40 minutes to catch our connecting flight. But everything was a mess in Singapore Airport. Read more about that here.
A part from that little inconvenience, it is quite modern airport.