Longhorn will have WinFS. In time, its not worth pushing back Longhorn for it and its not worth pulling it out completely - so it will be released at a later date. If indeed, its not released with Longhorn at the end.
Security Updates will range on the success of SP2; with more of the sort of efforts which brought out Microsoft Anti-Spyware. With a superior Firewall and more integrated Anti-Virus Protection possibilities for Developers who sell Anti-Virus Protection.
The 3D GUI; is great. Its not 3D... but its damn good nonetheless. Graphical Updates ranging from new icons for everything, based on more dynamic images for superior stretching to vast improvements in movements - taking on great improvements from Graphics Technology which we all saw, I presume, when Microsoft showed off a newer Digital Image Suite with Longhornesque Graphics.
Again, superior Networking and Internet Capabilities - which we're all waiting for from Internet Explorer!
Which is going to have to be damn good to beat Firefox with the growing support it is getting. Possiblity MSN Explorer-like in programming and design; but less MSN based to stop the federals from pulling Anti-Trust on them. Obviously MSN will be working on a Toolbar of sorts for this new Internet Explorer - probably now
They may be helping with the Explorer themselves.
Vast improvements for Technological Advances for Developers, Media Player Technologies, Integrated Searches like MSN Desktop Search, Outlook Express advances.
And so on... and so on and so on and so on....