Longhorn is a looong way off, so much as its entire File System System (hehe) has now been dropped from Longhorn as "too big a project" - its truely exciting stuff though (really).

Longhorn will be released in 2007 on MSDN, ive got the CTP build now - but the longhorn released will be a cut down version of the CTP !!

Basically it comprises of:

Indigo (the User Interface, much like the sony viao laptop User Interface)
WinFS - the bit thats been officially dropped (The new file system, which is like AD and sits on top of NTFS v5 - basically it allows you to store many many more attributes with a file, most of which is automated. So say you were in a meeting and they said "Bob wrote his requirements to us last week" - rather than having to ring bob and him search for the file, you can just do a AD search for documents from bob to whoever and it will get it for you, its very clever indeed).
WinFX (new fangled API)
1 more I cant remember.

The good:

Great content management, automated and actually does what u want (unlike the Office automations).
Really Really good UI - Windows has had a shit API for years as far as Im concerned - solaris' multiple desktops are my personal fave.
Fast Loading and really really quick indexing of files and SAM management.

The Bad:
Indigo Shimmers a lot at the moment and forgets where u last were (hard to explain, but a bit like setting a folder view thats always forgotten, and pressing up a folder and going to somewhere completely random).

The Digital media system is far too intrusive and if u take an image off a CD, you can burn it as many times as u like on the local machine, but CANNOT burn the image if transferred to another machine (may kill peer to peer - *faint noise of Woz cheering*)