Used it today, I had a little trouble with the plunger as well but overcame it with brute force, it now squirts in any position. Put dose into barrel then filled with water, that was a mistake, consequently I think the dose was a little lower than it should have been.
I did notice the brush seemed quicker across the glass. On a top window there was a large and quite old bird mess that the owner said had been there for weeks maybe months, sheltered window. I whizzed round as was in a hurry this morning. Forgot about the mess so went back to find it was perfect. Luck, not as bad as I thought, well I`ve never had it clean as easy as that. One of the windows is very phobic, now the water didn`t sheet all the way down the window but the area that it sheets is plenty for you to know it`s been rinsed properly.
One bug bear was the bubbles, I kept thinking they were particles on the glass. Wasted time with that but that`s me. Not as brilliant as I hoped but the dosing was wrong I`m sure. To sum up the rinsing is worth it on it`s own so I will be buying again.