I think because it isn't a click away, and users shouldn't have to trawl google to find the way of downloading apps to fix the fact that MS think they are doing a good thing.
Java doesn't work in metro, it tells you on their website. Tells you to use the desktop, but you can't access half of what you want to do in metro, like auto detect drivers for your nvidia graphics card. Catch 22 situation. How do I get to control panel in desktop? Without downloading a third party start button before hand.
You need the metro to do basic tasks, like control panel. Which is impossible to find because of some newly created pants menu system that is bold and brash but isn't control panel, the real one is a long type away. So you ahve to save your shortcuts by pinning them everywhere and doing the same as control panel but littering basic functions across your desktop. You can't just go start - and do it. You now need to go start - and then metro and then type, adding time for basic functionality.
Full screen is god awful in metro.
Nothing is where it should be fair enough, but to quit out of the machine you used to start - shutdown. Now it is go right a bit, wait for the menu, click the cog, wait a bit, then click the power, wait a bit, then click the power off. Talk about time wasting.
Desktop isn't desktop and task bar isn't taskbar, if it was what is the slide up left and wait a bit then another menu appears just like android 4.1, showing you all currently open windows. Does a program ever actually close correctly?
The advanced options are dumbed down considerably. Not just in control panel but the so called partition manager, which stealthily hides the reserved partition where you are not told, thus making a mockery of where you want to install your OS. Granted most users won't care, but as a system admin I care.
3 internet versions of explorer, but they don't transcend favourites the two ways of accessing your data.
Navigation is a night mare as there is no real demo, does the icon mid way on the ghostly pop out menu mean take me to desktop or metro, I will try it, of it's metro, so I now click on the icon to get back to desktop. Why can't I just go back to desktop. So a three step instead of one step process.And what is the three spinning thing that looks like yingyang, is it homegroup, I am not sure?
Search should be a tool, not a requirement.
That was my first initial impressions.
A Ui is about getting things done, not about having to type everything in a search field when you should just be able to click.
Yes you can spend three years dicking round with tiles and squares to put them in a nice order, but if you like a clutter free desktop with folders of your documents then tough, the metro is useless because it just sticks them there in a nice long list, but they are still squares and awfully garish.
To me it is two OS Ui systems which shouldn't exist on the same thing. One for desktops and one for the surface. On a Pc with a mouse it is a lot of movement (I have a 24 inch monitor) for little reward.