I've had it done, it cost me £1085.
Payne told me that if you've had it done once, and it didn't work, it won't work the second time. It will always give you a couple of months worth of dryness - which is why some people choose to have it done regularly to enjoy that sensation - but after those 4 months you'll either start to sweat excessively again, or sweat normally. If it doesn't work, you'd be much better with botox rather than have retrodermal curettage all the time. Still, Brunette, the operation you had might have been different, so retrodermal curettage is still probably worth giving a go.
For me, at the moment, it's worked like a charm. I sweat normally now and I've not had a single sweat patch appear (aside from a tiny tiny tiny tinnnyy one that appeared after walking to and from the clinic... which takes about half an hour each way). I really do hope this lasts, it's such a relief. I suppose even if it doesn't there is always botox as a last resort.
Incidentally, Payne is a sound fellow. He gave me some information that basically related Hyperhidrosis and blushing to a blood dilation problem, which explains why people who sweat also tend to blush. Good luck to everybody having it done!