I've had two, I briefly had an S147 "stick vac" (very heavy for a stick vac too), bought for £5 and sold on a week later a few years ago, and I currently have an S316i, paid just £10 for it, used of course, and while it's not electrically broken down since I rebuilt it, the plastics have been falling off all too often, to me, the build quality is like that of cheap store-brand vacuums, but sold at a high price, I can't even change the bag without the lid falling off, and of course the tool door hinge was not well designed, so that's loose due to one side breaking off, the filters are a joke, and the hose (which I believe is still supplied with some current models) has so many joints in it that it loses a lot of airlow long before the it gets to the floor tools...
Also, the size of the bags when you look at the price of a pack of them, it's ridiculous, plus the small bags, which are meaner than a yorkshireman, means you have poorer airflow than if you used bigger ones (I managed to fit a generic Kirby bag in my S316i, and the airflow improved dramatically) hence why I've got GN bags in an FJM model, and if you look through the archives, there are some models that have issues with some of the bags which are supposedly meant for those models, but end up not being so, and thus leak all over the inside of the vac...
So all in all, in my opinion, Miele vacs are not really worth the money they're sold for, I'm just glad I never paid the original retail prices for my two...