A guttervac looks like it might be a useful bit of kit to have. Buying a complete kit isn't cheap.
I'd been thinking about this and come up with what might be (although it might not be) a cunning plan.
A local hire centre hires out an 80 litre, 3600 watt machine on a wheeled base at about £20 a day/£48 per week. This machine has a similar specification to the guttervac.
I was planning on putting together a few sections of 2" drainpipe with a J on the end which should fit onto a 51 mm suction pipe and attaching that to the machine. Something similar to the pipe on the Upkeeper.
There's a video available on their website:
www.upkeeper.co.uk/gutter_keeper.wmv though you might want to turn your speakers down.
Hire a machine for a weekend and just have a play with it and see what needs to be done to make it work whilst clearing out my own and other unsuspecting family members' gutters.
Then, if it's a goer, put a week's work together and hire the machine for a week. Do that a few times and see how it goes. If it's OK, invest in a machine of my very own. If it's only moderately successful, keep on doing the odd week here and there and just hiring it when needed.