Some Ubuntu 12.10 Quantal Quetzal have been dropped for Ubuntu 13.04 Raring Ringtail. The most important Quantal apps missing from Raring are gksu and friends-app. Also, you can downgrade the Nautilus to the Quantal version.
1. gksu:
If you are not a terminal maniac, you must use the Alt + F2 combination to exec commands. When needing to run applications as root, type prefix the commands with gksu, example: gksu gedit /etc/shadow. Because gksu is not included in Ubuntu Raring, just type in your terminal:
$ sudo apt-get install gksu
2. Friends-app (the old Gwibber):
Gwibber was not included in Ubuntu Raring, because it was in the process of rewritting from scratch by the time Raring was released. The new Gwibber is now called Friends, to install it do:
$ sudo apt-get install friends-app
3. Get back the Nautilus version of Ubuntu Quantal:
This is an experimental patch that may break your system. It depends on you if you want to install the patch and risk to break you system:
$ sudo add-apt-repository ppa:webupd8team/experiments
$ sudo apt-get update
$ sudo apt-get dist-upgrade
$ sudo killall nautilus