It's no good asking people who have them, when you've spent £15'000 on something you don't turn around and say "actually everyone was right, they're not saving me anything at all". They have a placebo effect, you kinda just assume they're saving money because that's what the salesman told you. But I think even at current rates, 15000 in the bank is going to collect more interest than it'd save attached to your roof.
They're also becoming a bit like conservatories, once one person gets one, the whole street has to keep up.
Even in mid summer, with full light on them, they're not enough to run a high power appliance. What you are in fact doing is paying to have your house used as a solar generation point. You don't have batteries, so your not storing what you generate.
If someone came to you and said "we want to stick a wind turbine in your garden", you'd say "hey, f**k off, not unless your paying me.......", equally if they wanted to turn the neighbouring field into a solar farm, everyone would be up in arms. But with some clever marketing they get almost exactly that, only you pay them for it.
Solar water heating on the other hand (much more efficient that converting light into electrical power), that could be a massive money saver and really quite easy to DIY the panels with the raw materials. I've actually done some initial experiments and managed to heat half a litre of water to near 170c in just short of 1 hour. Whilst my solar power experiments have been nothing but a disappointment.
I'm all for being "green", but lets do that by making stuff last longer, instead of ramping up production of consumer goods and making them last less than half as long as they should.
Just my 2p worth