So, the 'special surprise' that was trailed is, in fact, a Hi-Res Texture Pack. I can live with that! I'm looking forward to seeing Skyrim in the full texture resolution that it could have been in, if it had not been held back by the outdated technology of consoles
From the release notes
Experience The Elder Scrolls V: Skyrim as you’ve never seen it before with the Skyrim High-Resolution Texture Pack. Make sure your system requirements exceed Skyrim’s recommended specs before attempting to install, including Windows Vista or 7 operating system, a minimum of 4GB of system RAM and a DirectX 9.0c compatible NVIDIA or AMD ATI video card with at least 1 GB of RAM and the latest drivers.
My specs exceed that, so I'll certainly be upgrading
Just had a quick trawl on Bethesda forums and there' s already at least one mod uploaded made with the Creation Kit
Emma, who made the totally awesome Vilja companion mod for Oblivion, has uploaded a modest house mod. More importantly, the fact that Emma is modding gives hope that we'll get a mod that does companions properly.