I'm loving the previews of Leopard.
When I saw the screen shots of the 'stacks' thing I thought - what a gimmick - I'll never use it - but when I saw the keynote and saw it in action I changed my mind - really cool.
iChat - as I am unable to use iChat with anyone else - it didn't really do anything for me.
Spaces is such a cool idea - love using that sort of thing in Linux.
Time Machine looked outstanding last time I saw it - sounds like it could be a real handy tool core animation looks wicked - liking the cover flow thing - It all looks great - I found my self to be very impressed by the WWDC keynote - just because of what we were being told/demo'd about Leopard.
The preview thing was really good - especially the way it handled PDFs.
Thought the iPhone stuff was a bit rubbish though - making apps for iphone using a browser - sounds like a cop out to me.
I'm looking forward to it [Leopard] - money will be put aside sometime soon