We flew from Miri to Mulu aboard a small Malaysia Airlines plane, in around 15 minutes.
In fact, we flew all over Borneo on their planes. We always booked online before we left home.
They were always on time and very friendly.
It is very easy to get around the cities of Borneo. If you purchase a good detailed map you have no problem finding your way on the back roads either.
We rented a car most everywhere that we went.
From the ferry terminal in Palau Labuan there are express boats that leave several times daily for several of the islands. We took one of the boats from there to Bandar Seri Begawan.