To save you reading to the end, let me summarise this review in two words: GET ONE!
Karcher are well known for one of the most time-wasting products ever invented by humanity. Their range of pressure washers will get your patio so clean that you can lick a gallon of split milk off it and suffer no ill effects. Does your outside space need to be as clean as a cat's rear end? No it does not, but once you start you will encounter two issues: Firstly, you will have to clean your entire multi-hectare estate since the newly clean bits will make the not yet cleaned bits look like downtown Shanghai before the redevelopment work started. Secondly, the job is so satisfying that once you start you cannot stop. Hours will fly by. You will look for things to clean that do not need cleaning and have never been cleaned before. You will clean things that ARE clean. The wife will report you missing (or at least she would, were it not for the fact that the racket the pressure washer makes is a sure giveaway of your presence behind the shed).
And so Karcher turn their attention to your filthy, decrepit windows. You should probably be ashamed of yourself. You disgust me. Ask yourself a question though: Does some light come through? If the answer is yes, then your windows do not need cleaning but, let me tell you, you WILL NOT be able to resist the temptation. In ancient times, our elders would have wiped the window with a damp cloth, possibly dipped in a solution of washing up liquid, but whatever they did to remove the moisture their windows would have ended up coated with a slimy mess. This, I am convinced, is the reason churches went for stained glass since, in the absence of the Karcher, they could never achieve the smudge free cleanliness they so desperately desired. Even the Romans tried various innovative methods to enhance the finish, such as using vinegar in solution or rubbing the window with a scrunched up Daily Telegraph.
Step forward to 2012. Wipe the windows...suck the excess off with the Karcher. I thought it would work well but I couldn't imagine how well. The finish is excellent. So easy. So satisfying. The one downside is the battery. A 20 minute usage time will let you clean your own windows and then you will be banging on next door, begging to clean their's too. But you'll have to wait two hours.Kärcher WV 50 Window Cleaning Vacuum