Some are actually programs supposed to help the user, but are real bugs.
The apport problem: the never ending crash reports is a bug, which the Ubuntu devs had not looked at. It is annoying. One can disable Apport problem by disabling it, but then one would never know, if there is a real problem later.
The Compiz matter: The plugins Precise had, neither Quantal or Raring has. There is no Annimation-addon and you can't use the 3D windows add on. In the development fervour, these had been disabled or made not to work, most probably the latter. When you develop and something goes missing, then it is a bug.
The Nautilus matter: Dual panes had been taken off the new nautilus, but Ubuntu should've given us the better, but old nautilus with the F3 option. There is no special need to abide by the ideas of the Gnome 3 devs, if the main UI is Unity for Ubuntu, so not allowing the "old" Nautilus to be installed is a system-wide bug. One might try to install the SolusOS patched nautilus, but that's not the answer. Nautilus 3.4.2 should be in the repos as a variant. This is a Raring case.
The Grub setup matter: It was pretty easy in Precise. You simply did sudo grub-seup /dev/sda, but in Raring (and in Quantal) this had been taken off. The only solution to set the Grub is by using a ppa, Yannubuntu's Boot-repair. Or else reinstall grub-pc.
Well, what do you think? Do you see any other bugs? The real annoying ones?
Seriously, Raring is better than Quantal or Precise. All these days, Ubuntu had warned us not to use the coming release on production machines, but that warning is now gone and you can download a daily, which is good as the devs are now very sure of their distro.
In my case, I don't think that Unity is a necessary evil to live with. I don't ever use Unity and search for other UIs. I've found one, an old one, which is practically discarded, because of its universality, one that has no binding with a given WM or DE. (Devs appear to be unhappy with universal applications, so the go looking for others, such as Gnome-shell, Unity, Cinnamon...and taking away the right-click...)
When an ability is taken away, the whole thing becomes a bug.