I`ve had the backpack from Window Cleaning Warehouse for nearly three years. I`ve totally abused it, left for over a week without charging and dropped it countless times. It has broken down a few times but nothing I couldn`t fix. It`s had a new speed controller, two new outlet pipes, down to abuse, and a new switch.
Also remember that except for a few exceptions they are all Kobold components.
The wish list for the backpack is a better handle to carry it and lighter water when filled but other than that it`s great.
I did consider buying Gardiner`s which is cheaper but sticking with WCW.