Seems a good price for a flat. The commute to work isn't so bad as the ferry is comfortable, reliable(!) and gives a nice 30 mins each day for some admin, reading, studying - or just relaxing!
The commute back is more of a pain - especially if you head out at night. Of course it is possible to cab to Tung Chung and then Lantau cab to Mui Wo but costs about $400 for the whole trip - and takes around 45mins to 1 hour. Be sure to book your Lantau taxi while you are in your HK taxi, as there are probably no taxis at the Tung Chung rank late at night (or early morning!).