Regina 3D Launcher
The Sensation comes with Sense, HTC's custom Android launcher. Sense is arguably the best of the custom launchers, but it's not everyone's cup of tea. That's why there are multiple launchers available on the Android Market that dramatically change the appearance of your Android phone's user interface. Some popular options are Launcher Pro and ADW Launcher.
However, a powerful device like the Sensation can flex its muscles with a 3D launcher which makes use of the graphics capabilities to provide a smooth, interactive, beautiful interface. One great, free option is Regina 3D Launcher.
Regina divides your phone's interface into a number of "workspaces" which are similar to the homescreens found in other launchers. These workspaces can be browsed with a 3D interface, however, which means you can see all the workspaces at once without resorting to excessively miniaturized versions of each. Another nifty feature is the hidden workspaces, which can be only accessed if certain conditions are met.
As said, Regina is free, and it looks cool. Even if you decide not to use it as a permanent replacement for Sense, it's a neat app to show your friends.