Ubuntu 13.04 has a few new features that are welcome, but you might also experience a few glitches too. For example, you can't upgrade from 12.04 to 13.04, some people have had performance problems running Ubuntu in VirtualBox and so on. Here are the answers.
If you already run an older version of Ubuntu Linux you might have tried to upgrade to the latest version, but discovered that you can't. It simply isn't an option. What you have to do is upgrade to the next version, then the next and so on until you get to 13.04. For example, if you have Ubuntu 12.04 you will find an option to upgrade to 12.10. Once you have done this, if you check the Software Updater you will find that there is now an option to upgrade to 13.04.
When Ubuntu 13.04 was installed in a VirtualBox virtual machine, it ran very poorly. Not everyone has experienced this problem, but I am not alone and there are a few others. Using the latest version of VirtualBox and the latest version of Windows, Ubuntu was so slow it was unusable. Running System Monitor showed a high 65% - 75% CPU usage and screen updates were very slow. You could see the frames of animation as menus faded in and out.
A variety of settings were tried, but none seemed to solve the problem. The solution was to use different virtual machine software. VirtualBox isn't the only program of its type and VMware Player does exactly the same thing. And it is free for personal use too.
The interface is different to VirtualBox, but the settings are more or less the same and it works in a similar way. Getting Ubuntu up and running in VMware Player should be straightforward if you have used VirtualBox. Download the Ubuntu .iso image, create an Ubuntu virtual machine, attach the .iso file as a virtual CD/DVD-Rom drive (no need to actually write it to a real disc), and boot it up. Ubuntu installs and runs fine with none of the performance problems exhibited in VirtualBox.
You can add online accounts in Ubuntu 13.04 and this enables Ubuntu software to access things like Twitter, Facebook, Google Contacts and Picasa Web Albums and so on. Google works fine. Twitter worked for a bit then stopped, but a clean install started it working again. Facebook simply doesn't work for me. Not on an upgraded Ubuntu PC, a PC with a clean install, or Ubuntu in a virtual machine. I don't know what the problem is or anyone that has found a solution, yet. I'm sure one will come along eventually, probably in a software update, so keep checking.