1) If you are habituated to use ubuntu 11.10 with compiz ubuntu 12.04 will be your night mare for sure. It does not go well with compiz
1) To get all the applications in all workspaces (super +w) with scale and text filter make you get your required application instantly.
In ubuntu 12.04 this behavior is removed which will display the applications only on the specific workspace which you are in which will work only the second time. First time all the windows will disappear.
Even the ring switcher plugin will not help you to get back your applications as this plugin was also over written to show only the applications of the workspace you are working in 😦
Try to activate application switcher plugin unity will crash
2) There is no smooth switching between workspaces monitor flickers every time when you tried to go to next workspace which is quiet annoying
it is not resolved even in ubuntu 12.04 LTS version
3)If you try to install from pendrive it will take ages, you even don,t know whether the installation process is going on or it stopped working for some reason. Even the installation process from CD-rom will take more time than 11.04 , and more over insert the cd and wait for atleast 15 minutes to get the installation menu.
4)atl+tab behaviour is funny, cannot explain in my words 🙂 try it out your self
5)The default settings will not hide your unity launcher even if you try to maximize your terminal or any other window.
I find no apparent reason why you want your unity launcher to be shown all the time with your maximized windows.
when you set the unity to hide in the settings menu, result is disaster, you will not get the menu when you needed.
It is really fun when you have multiple terminals open and try to see the terminals when you point your cursor on the unity launcher.
In performance i did not find any difference between both. (try to google it you will see the benchmarks with no differences) bit lazy though
6) This is not a disadvantage but it would be better if ubuntu gives a default set of wall papers which are atleast are good as mac of windows 7.
All the wall papers are close shots of your pants or some thing else, which will not fit in present day led monitors.
7) cannot have the an encrypted home folder if so, you will get this error
8) An alt+tab combination will some time removes the title bars of all the open windows which is a big problem in ubuntu 11.10 https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&ved=0CHAQFjAC&url=https%3A%2F%2Fbugs.launchpad.net%2Fbugs%2F874925&ei=29KnT9GvA8rE4gTrvtTQCQ&usg=AFQjCNHBqS9VhZu6Kbe7uz1IKPMNRrLMYw&sig2=0DuiSb6saAQJT_2mG_py6Q&cad=rja
( i have not tested in 12.04 as my monitor flickers with ATI radeon graphics card all the time )
9)When you want your application to move next workspace , instead of moving to next workspace, the given application will close with no further notice.
10) last but not least i was unable to login in to system when i tried a upgrade from ubuntu 11.10 to ubuntu 12.04 in my laptop instead of my home computer, which made me to write my first blog in my life
Hope some one out there will know all the possible failures before installing a new copy of ubuntu 12.04 and to be prepared for worse.