I've been using these for a couple of months. Very good. There are advantages and disadvantages over the univalve.
Such as ?
UnivalveProsNo learning curve.
More ‘certain’ as a shut off when loaded into the van (you could leave your pole connected all day)
Can be retrofitted to any pole on the market (except poles with exceed tubeless I guess??)
ConsNot as ‘fluid’ to use - more likely to not be used between windows
Additional flex in the pole hose makes it difficult to operate at height
Metal o-clip needed near the brush and therefore glass
Once fitted it's not easily stipped out (a pain on frosty days)
Gardiner’s valveProsMore fluid in operation, once you get the hang of it turning the water off between windows becomes natural
Saves more water as used more often
Seamless integration on our SLXs
Can be used while in operation without removing your hands from the pole (handy for wiping vents that you don’t want to get wet)
Easily stripped out for defrosting
More "complete" product. None of this o clip bodge business.
ConsFlex and/or wear in the pole/clamps makes it difficult to work at height especially on velux windows and windows off at an angle (i.e. above conservatories)
Learning curve (about 1/2 an hour for an decent lad)
More prone to blockages - (we've had about 6 in 2 months. Very easy to fix though)
All in all there is not too much in it. Some of our boys prefer one, some the other. Most weren't bothered, they do the same job with a slightly different technique. If I was out cleaning windows, I'd have the gardiners, it makes for (slightly) quicker cleaning and saves (slightly) more water.