Research the subject on the web!
There are a lot of opinions in both camps, ie it's useless/the best thing since sliced bread. Most 'for' views are a variation on 'I've spent a lot of money, so it must be good' with very little science backing them up. I did read a very technical 'against' web page but it has to be said, the writer had a financial interest in a competing product.
I'm in the 'useless' camp as I understand the heat capacity of the liquid to be less. It is expensive, and so is the stuff to dry out the system you need to flush with too.
I believe Uncle Melvyn sells it, I'm sure I saw it in one of his advertisements in Miscellany.
