Surface/Arm != Surface/x86. The former family was (finally) shot and laid to rest the latter family sells quite well and is making money for MS quite nicely. Not to mention proding companies like Lenovo/Dell/HP to produce updated versions of their units and improve while keeping a certain price range.
As for "great interface" - well if one likes cleaning the screen regularly and use an OSK instead of handwriting on a tablet then Apple did. Otherwise all they produced was another content consumation device and others did THAT better (but did not market it well - see Nokia N770/800/900). For productive use - even a Win7 Tablet PC with Wacom/Ntrig beats an iThingy