Everybody was waiting for this SDK, and a lot of people run to the developper.apple.com site. So it was a bit difficult to download this SDK but now I have it on my computer. Unfortunatly I haven't got a leopard, Mac OS X 10.5 computer, so I can't test this SDK but when I'll have it, and learn Objective C, I will give you my feedback.
You can, like me, console yourself with watching the video of the presentation, on www.apple.com, and it seem's that's the SDK is pretty good, rather game oriented. We can see a stars wars like game which use the internal accelerator to move the aircraft, and Sega said they've ported a game to the IPhone in only 2 weeks, pretty cool !!

So while waiting a leopard computer, go and take a look on the SDK Documentation which is available online
I'll be back with my first Hello World App on the Jesus Phone