Yes, the Al casing makes a big difference as it's much more durable. The 15" titanium's are currently painted. I have read dozens of posts of people who have had awful problems with the paint peeling, bubbling, and chipping away.

As to other improvements - hard to tell. I think there will be mostly design improvements. Aside from the updated casing and the 15.4" screen, I think you'll likely see improved airport signals (people have reported problems with the current attennas). They will also probably go to a single hinge along the back ala the iBooks and other powerbooks and probably move the ports to the sides - something very useful IMO.

Whether it comes with Airport Extreme and/or Bluetooth built in, I'm just not sure. These come with the 17" and I am sure Apple will want to keep a few things standard for their top of the line. Same goes for the backlit keyboard - could possibly appear on the 15".

Edited to add: given that it's almost August and the new OS is about to be released, I wouldn't even be surprised to see new 15" ship with Panther.

[This message has been edited by StudentExplorer (edited 07-10-2003).]