Shark..
They got the features right, made a vacuum for how most people tend to use vacuums these days. Because of this many of our customers don't want to replace them even when they do break and will pay handsomely for repairs. As such I can say that the construction of the machine is rather poor. They are actively making it difficult to repair and have longstanding faults that they seem to have no interest in fixing. The lower hose assemblies split after a couple years on almost all of them. The micro-switch in the power heads fail, the board in the power heads also fail, though that seems to have gotten better. Shark also uses security Torx screws and even counter sinks them as most people only have a standard short bit set. Replacement of the cord is a horrible process on almost all of them, and will never approach factory fit and finish due to a strain relief that is a weird custom shape.