We do a LOT of gutters and 3 years a go got a vac and it was the best thing we ever did!!
The nozzle does get blocked, you do have to clean it all up but IMO its all way way worth it!
We charge £40 for a 3 bed semi and can knock um out in 20-30 mins depending on build up sometimes even quicker if its all loose stuff and not grass and trees growing.
When we bought the vac we also got a local leaflet dump, glossy double sided printed and sent out to a few thousand homes and it paid for itself after month two, including the cost of the leaflets and delivery!!
Round here people seem to like it as its safer and you can get to the hard to reach places which ladders cant.
We also give a lot of ppl a call a year on to see if they need doing again as most just say yeah do it, its even easier then!!