they really ruined the UI, they removed windows classic UP meaning you get the task bar that is taller than the windows classic taskbar but shows the same info (less efficient)
Without using the tablet UI it is extremely hard to get to any control panel options
they got rid of the start menu, this forces you to move all programs either to the desktop as icons or to the tablet UI as tiles
it also relies on horizontal scrolling making it very hard to find any program. (imagine if you had as many programs on your tablet or smartphone as you did on your desktop PC. then imagine finding a program that you want to run)
while it has a search feature, they moved it from the start/ tablet area, and instead made it into it's own search tool that you launch separately then search for the app you want. which is a issue because that implies you know the exact name of the program. (not everyone knows the exact spelling or name of all of their programs, they just recognize the program when they see it and windows 8 removes your ability to do that)
Basically what Microsoft did was take the windows phone 7 UI and made the standard windows desktop UI into a app that you launch.
They also got rid of the back buttons so if you use their poor excuse of a start menu, you cant go back so suppose you are trying to get to a certain setting and you don't know exactly where it is. if you mistakenly click where it isn't and you are 4-5 menus deep, you cant click back, you have to instead close it then head back to where you were before clicking on the wrong option.
a fresh install uses around 600+MB RAM on a system (virtual machine) with 2GB ram
If you set the VM to 1GB, it uses 400-500MB RAM
While windows xp only uses around 30-40MB (when you disable the extra crap)
I urge everyone to test windows 8 in a virtual machine and see for them self how difficult it is to navigate.
and it has nothing to do with a learning curve, it takes more steps to get too virtually all OS related settings compared to windows 7, and even more compared to windows xp