I'm in Australia and have used solar hot water systems in number of locations and houses I've lived in, and also looked very closely replacing off-peak electric systems with heat pumps. Whilst the running cost is terrific (almost zero in most locations futher north than Sydney), and all the systems I've used have been very reliable unfortunately the capital cost/depreciation still make it a bad investment.
The economic comparison is to our cheap local electrical supply from coal fired power stations - even when you add in the subsidy that most local councils will give you to install solar. I haven't personally compared with gas but have been told its even cheaper than electric supply.
On a whole of life analysis I'm not sure even a "green" argument stacks up, since I suspect the capital cost of solar is something of a reflection of the energy used in manufacturing the equipment.
So does it work? Absolutely! Is it cheap? To run yes, to install no. Is it better for my grandchildren? Don't know.... requires a serious analysis