To clarify, a vac won't always unblock the downpipe. Sometimes it will and it's very satisfying when it does. But sometimes a weed has taken root deep into the pipe and no vac can get it, be it 1500W or 3kW.
But it should be mentioned that these are quite rare. To discount a 1500w ladderless vac just because it won't do 1 in 50 jobs is like saying you'll never use a toaster again just because it once burnt your toast.
Ladderless gutter cleaning is becoming more and more popular. It's a 'lightbulb moment' solution to a universal problem. A handful of jobs it can't do. But most it can and like Colin I'm enjoying the current demand and expecting strong growth.