A combined washer/dryer will have an even longer cycle time than a separate washer and dryer, since you can't start the next washing load until the drying is done. In any case, some front loaders have wash times comparable to top loaders (Choice magazine tests include wash cycle times).
Choice profiled an LG combined steam washer/dryer in the Aug 07 issue and they noted that it used 74 litres of water on the dry cycle (it uses water to condense steam from the hot air, so it doesn't have to be vented), in addition to the water used on the wash cycle.