this is my opinion on hot, which i have been using for over 2 yrs, with the l5.
in the winter i have it set at the minimum heat, just luke warm.
the windows, i find are just dirty in the winter not covered in fly spots, spiders pooh and baked on bird pooh etc, so the warm water is just nicer to use than cold, no cleaning advantage.
but in the summer when all the above are common place you can turn the heat up which will help you clean.
if, like now, the weather is bad, the water will still probably freeze on the glass even with hot, so i dont want to go out in it anyway.
my conclusion is i like using hot/warm water rather than cold, because i know when i run out of gas i hate just using cold.
as my complete hot set up only cost about £200, i think it is well worth the money, and the running costs for the gas are only £30 p/month.