That does seem a little bit pricey but I haven't seen one being used, so what do I know? I use a very stiff brush on a long extending handle that I originally bought to scrub off my conservatory roof, it was about 20 squid, sorry no pics or links, but it is very effective at clearing the scum off the waterline and down to and slightly below the chine. Also does trim tabs, rudders and props.
Yes , got one . Any good, only for keeping waterline and just below clean. Needs buoyancy to apply friction and this forces the whole kit sideways. You need to be on a pontoon or dock.
I have used one. It does a useful job as long as you haven't let the boat get too fouled up before using it. It is good for slime and weed, but gets torn easily on hard fouling. The shape and the buoyancy are what make it work better than a standard brush on a long stick. If used regularly, it is probably worth it. I never managed to scrub 100% of any area in any one time, I used to look at teh results with a camera, but regular use would mean every bit of hull gets a scrub, but some bits maybe only every two or three scrubs. This is why you need to do it often.
Brilliant, however its brilliant because I have round bilges. when it comes up to an obstacle it stops, so if your hull is not smooth and round it might be a bit tricky.
I was on the boat for a couple of days this week, and with summer holiday coming up it seemed a good time to remove the last few months growth, probably takes 10 minutes a side to do and that's on my 31ft boat. Notable 1 to 1.5 knot improvement on the previous weekends normal cruising speed.
edited bit;
I would add, I just slackened off my lines and pushed the boat away to do the pontoon side. and jumped in the dinghy to do the other side. I did wonder how easy it would be doing it from the dinghy as normally I just turn the boat around but actually it was fine.