HTC Desire HD is the first 4.3" Android phone to arrive in Europe, so if you're in Europe and you've been envious on Americans for having the Evo and Droid X, then this is great news for you.
Desire HD will come with Android 2.2, which is to be expected by now, and will also have the new HTC Sense with a few extra apps and widgets. It will feature the new HTCSense.com services that will help you remotely wipe your phone if it gets stolen or simply lock it and send a message to it that you're offering a rewards. Some of the services there could be really useful, and I think this is the direction manufacturers should follow instead of skinning Android.
They should offer customized services and use them to make people come back to their phones. They should stop skinning Android beyond recognition, especially once Gingerbread is out and it should have a great, or perhaps the best mobile UI around, if WebOS is any indication of what the new UI lead at Google can do.
Here's the unboxing of Desire HD from Slashgear: