I've recently had two experiences with UIs that are designed to be streamlined and user-friendly. And, frankly, to me they're anything but that.
Windows 8
For some reason I had to use it and well, it took me several minutes to figure out that the loading...-like screen is actually a log in screen and I need to click a nearly invisible single-coloured button to actually allow me to select (or write) a username and log in. Then it took me another several minutes to figure out how to find Desktop. During my work I was several times greeted with IE instead of Start menu (who the hell did have the idea to put an IE icon next to a sensitive corner that gets you to the start menuscreen?) and found out how to log out by sheer luck. Didn't figure how to shut down from logged user. Ugh, I have to tell, GNOME Shell is heaven compared to that.
Fedora 20 Installation
Everything is parallel. I have to say, I prefer the linearity of the old Anaconda. Just clicking next, next, next and nothing gets missed... Now, well, that's another question. The icons being single coloured didn't help much either. I just hate these new symbolic icons that the PC world of nowadays is plagued with. E. g. here on blogger I always confuse pencil with label. *Sigh*
But well, having to spend 30 mins on custom partitioning and only figuring the problem after reading a manual, when it was actually a something the installed could have told me itself, is a completely another story :( Why does the new anaconda tells me the partition is not correct, but does not tell me why. Why? Why? If it knows it's not correct, it should tell me the reason, not just pop up a bubble telling me something is wrong, that Fedora needs 5 Gigs of space (which was perfectly satisfied by the configured layout) but not telling me, that the problem is missing /boot/efi partition?! Something that's was obvious to the installer but not to the human encountering UEFI for the first time... Why it cannot tell me the error it encounters? Why? Why are all the new UIs pretending human is a brain-dead idiot with less intelligence than a well-trained monkey?
But to end it on positive note, F20 on Live USB is freakishly fast as well as the actual installation :-p