Never used before but if anyone does, its going very cheap at ASDA - normal price £4, current price £2 for 500ml spray.
Bought three, hope its OK.
I think most everywhere else its around £7.65.
Having just bought RainX got home to find our local BMW agent (Rybrook Warwick) is offering a windscreen treatment which repels rain and sleet etc for £29.99.
Treatment is demonstrated on this:
If you have RainX windshield washer fluid in the UK it works pretty well.
The best straight glass cleaner is the GM glass cleaner (AC Delco), also sold as Bon Ami . Doesn't do anything to repel rain but works great as a cleaner.