Hi,
I just came back from Sipadán on Celebes Explorer liveaboard.
To sumarize, diving is just impresive but anyone considering going there should have two things in mind:
1. The boat is the best way to dive there, but bring food and cleaning for the WC.
2. Diving in sipadán is limited, so whatever they tell you in advance about the posibility of diving the full week there, once you arrive will be transformed in 4 days diving at Sipadan, and the rest in other places not at the level.
Please, feel free to ask if you need further information.
Regards,