XDA Developers have taken the latest YouTube application bundled with the HTC Touch HD, which is a WVGA device, and have successfully ported it to VGA to fit the Touch Diamond and Touch Pro.
The new YouTube application, version 1.6.1820.4128, is available via Full (which basically installs the whole newer app) and Upgrade (which will only install the main executable and registry files) versions. Whatever you decide to go for, install to Device and soft reset after installation. Author notes that “the main difference is the option to select “Programguide”, like Comedy, Entertainment and so on…” and also advises (so do we) to make a full backup of your device before installing.
Note: Some newer Touch Diamond and Touch Pro ROMs might already include the latest version of the YouTube app. To check if it’s your case, simply look for the Programguide inside the application or open a registry editor and go to YouTube inside HKEY_LOCAL_MACHINESOFTWAREOEMMASD.