Very commonly used in places like Singapore and Malaysia but there generally you don't want too much heat in your hot water. Confuses people the first time that they have to turn the switch on outside the bathroom first.

Where it becomes a nuisance I find is that because there is no central hot water, there is not hot water in the kitchen (without boiling a kettle) to wash up. Commonly also the bathroom basin isn't connected either (i.e. it's just the shower) so if you want a decent shave with hot/warm water you're out of luck...