From a thread over at appleinsider....
First off, what I'm about to say will probably be regarded as BS, lies, and more lies. I'm positive about the information and have, and even if you don't believe me now you'll get to see sometime after June. This is going to be a huge year for Apple.
You'll see IBM 970 64bit w/ "Altivec Velocity Engine Extreme"
You will see Mac OS 10.3 available on x86 Intel Processors. At first it will run in server enviroments only (because apps will need to be recompiled with a simple tool) Later on you will see apple release it for sale with certian OEM computers. They have a way to limit it for testing acceptance to only those OEM machines. If it goes as planned OS X will sell to anyone with a x86 box. This wasn't ever supposed to actually happen, but the CEO of Intel has been pushing Apple's board of directors really hard on this.
There is also OS X 10.3 being ported to the 64bit offerings to be forthcoming from AMD. I cannot confirm it this version of OS X will ever be released.
Some Details of OS X 10.3 (some of you probably guessed these)
64bit OS, including rewritten finder to take advantage! Jokes have been made about "finder extreme".
Multiple concurrent GUI logins (similar to XP but with solid unix)
OSXFS - New filesystem, based off of BeOS Filesytem. Very cool features built right into the finder! 10.3 Includes the ability to lay windows out with rich HTML based on the webcore. You can use "simple/regular" finder mode to bypass these. The ability to assign files categories like ID3 tags. Ever finder window can be searched realtime similar to the itunes search thanks to OSXFS. You can find all files that were assigned "category" business in 1 second flat.
New Print Services and much better dialog windows
New Navigation services! Three different ways to drill down files, you can even click a button to "spot" the folder. This means your cursor changes and you can move through the finder to locate the folder then hit enter key to finish saving. You can also assign the file categories at this time or the application can by default. files created by apple sound track editor can automatically be assigned "audio", so could files from an updated pro tools.
Bundles (some of you call them piles) work sort of like this, you could select 20 files and say "these are all the files for my project" monitor them. when you go to move 1 file it will automatically copy the rest with it. You can also condense them to look like a folder. Think files on different hard drives, different networks all as one project "folder" all updating and all copying when you move them. Very cool.
New themes and sound effects, lots of interfaces changes, and customizations you can make for yourself
New dock, so many new features, split mode, text mode, "start menu" like mode for people who prefer windows. dock is very slick in this version, better than the start menu.
new quicktime, very very nice player, apple went all out! even supports nonstandard divx format and wierd avis, it's new billing will be "anything motion" (not those exact words)
new ichat, built in video conferencing (works with netmeeting!), voice chat, secure chat, better sortable and group lists, jabber support, plug in module support (for other IM services) and many cool new features and several mac only ones
new mail.app uses webcore for parsing html/mime email now, much faster and better, offers exchange server support, and many other new features, including a new "view" that looks exactly like outlook 2003 preview for windows. (you can still use old ones) mail is much faster.
built in ftp, sftp, scp into the finder connect to server menu.
much improved sharing controls for sharing with windows and unix enviroments, lots of complex options.
new built in remote access software, much better and faster than stupid remote access from apple. It reminded me of terminal server for windows. very fast.
new itunes (this will be out sooner i think) speed updates and built in support for music service?? new wireless and options to "share" your files with friends only on certian files.
new iphoto (very very very very very very very very fast)
new appleworks (new name, don't know if it ships with it, looked very nice!)
that's all i can remember.
http://forums.appleinsider.com/showthread.php?threadid=23296&perpage=40&pagenumber=2
Granted, every one seems to have "the inside scoop" about what 10.3 will contain. Regardless, this thread struck me as interesting.
Any thoughts?