IMO probably the best £90 (I've had mine two years) I've spent on wfp. If you get one first thing I would do is check the battery connections are tight.
I use mine for doing rears where it's simpler than using the van mount and on any property where I have to go through the house.
I have never worn it on my back, but find the top handle ideal to carry.
Downside is that there is only one speed on the pump, I have fitted a bypass back to the tank so I can regulate the water flow a bit better.