Valve has published a comprehensive list of all the known bugs encountered so far by the beta testers and their solutions.
Even if Steam seems to run beautifully on most Linux machines and especially Ubuntu, there are still a lot of bugs that need to be ironed out.
Valve has put together a list of known bugs that have various workarounds and which probably need solving before the release of a stable version.
We handpicked a few of the most important bugs that can be resolved, but you should check the official list to see if you find any relevant information.
• Installing the Steam for Linux .deb package on Kubuntu 64 bit requires gdebi. First, you need to install the gdebi-core package (sudo apt-get install gdebi-core) and then install the Steam for Linux package (gdebi steam.deb);
• Steam currently disables the (deprecated) XF86DGA mouse extension. This mostly affects games using the libSDL1.2 library. Games with libSDL2 use the newer XInput2 extension instead;
• The Catalyst 12.11 AMD graphics card driver is currently in the "precise-proposed" repository and hasn't been promoted at this time. This is part of a vetting process controlled by Canonical. You can enable this repository by opening [b/]Ubuntu Software Center, selecting Edit | Software sources... and then enabling the Pre-released updates option on the Updates tab.
• There has been an AMD driver release that fixes a bug for users running on an AMD Radeon HD 7000 series graphics card. You can get the latest driver by enabling the precise-proposed repository;
• For Ubuntu 12.04, the default behavior of the Alt key displays the Unity HUD. If pressed during game play, this forces the game screen to be minimized. The solution is to disable or remap the Alt key by using the Shortcuts tab on the Keyboard dialog.
Keep in mind that the current version of Steam for Linux is in beta and that bugs can be triggered very easily. Most of the problems can be solved by updating the drivers or by installing some missing libraries.