I have a V7 that my mother in law gave us and the cordless part is the only thing it has going for it. It doesn't do nearly as good a job as our corded Miele but it's good enough that I'll use it to spot clean when I don't want to lug that out.
I got a V8 after my old cheap handheld vacuum died, in part because I almost never could be bothered hauling my old canister vac out of the closet. (I have a housekeeper once in a while so that mostly takes care of the full-house periodic vacuuming.)
It works plenty well for my needs and it's so quick and easy to pull out and do a quick pass of a room or two.
I combined it with a Neato Robot Vac a few years ago and with those 2 I rarely have to take out my behemoth Miele vacuum anymore.