WE climbed the Pinnacles, yes they wer impressive but I dont think it was worth the hike. An extremely steep hike took us 41/2hrs up, longer down. Dangerous particurly when it rains which itwas doing, very slippy. ladders and ropes near the top. Use extreme caution.
Best to take the flight from Mulu to Miri.
Most of my tips will be listed under the country/city pages. However there is an universal tip for the island. Bring insect repellent! While there may be poisonous snakes and a few other natural dangers, the biggest danger is the mosquito. Dengue fever is not something you want to risk.