There is no HD video on the X8, I believe it was only the X10 that got that.
This was lifted from their product launch blog
The key changes for the different products are the following:
Xperia X10:
HD video recording with continuous auto-focus for high quality videos
Upgrade of the Android platform to Android 2.1
New back up and restore application, with extended content back up
5 homescreens for apps, widgets, shortcuts and folders
Social phonebook which automatically syncs contact pictures from Facebook and shows when your friends are online
Xperia X10 mini and X10 mini pro:
Improved Bluetooth functionality with support for sending and receiving pictures, contacts and more
New backup and restore application with extended content back up
Automatic synchronization of your contact pictures between Facebook and your phone book
Improved ways of handling pictures, audio, text and numbers in your messages
Upgrade of the Android platform to Android platform 2.1