I have only Nano-Cube 6g, my impressions:
- very good-looking and pleasant, not equipment is seen;
- fans and pump will hum with time,
- when cleaning chambers, you have to lift lid up - light will not lit the tank and chambers. Eventually removed the lid (as it's done with MH Viper lamp), much lighter and more convenient.
- non-photosynthetic corals are better to be kept in different tanks, allowing to have a separate flow and filtration.
In any other way - love it.