Under the hood it may be the most secure, most efficient OS ever, but that doesn't excuse making it a more complicated, less efficient experience at the user interface.
I'm talking of course about use on a non-touch device.
The keyboard/mouse combo provide an efficient way of working, and it would have been the simplest of tasks to make the two UIs optional choices depending on the device in use.
They may be stealing a large slice of the iPad market, and that's obviously their hope, but there was no need to do it in a way that alienates the enormous number of office PC users who are going either to hate finding that they can't work out how to do anything they're used to, or more likely, just decline to upgrade from W7.
Remember that most of the users here are at the techie end of the spectrum, and are able to hack the W8 experience to be what MS should have made an easy option. The vast majority of commercial Windows users are barely capable of more than "I switched it off and on again" to deal with a problem