Saw the whole thing yesterday evening. Streaming was fine, no stutters or pauses.
I thought Steve came across as atypically a little flat.... still good, but he didn't seem as dynamic or self-assured as he did at MWSF. I don't think it was because Leopard didn't have the goods either... it was funny but he didn't seem to do that great job of pointing out why Leopard was good.
For example, from folks who are using the WWDC Beta of Leopard, apparently the thing is damn FAST. No more beachball. Browse network shares like lightning. Better multithreading. Finder is all-Cocoa, finally. No mention of any of that from Steve that I can recall.
Even when he was demoing things like Quick Look or Coverflow in the Finder, he wasn't saying the obvious but necessary-to-say things like, "Hey you can check out all your apps without launching them- isn't it great to have an OS that doesn't slow you down? Can work as fast as you can? Saves you time?" etc. etc.
He said the first part (preview and even scroll thru your docs w/out launching) but didn't hit the benefits/implications of that. Maybe its because he was speaking to developers and didn't want to insult their intelligence (to THEM, the bennies are obvious), but he had to have known that there'd be a much broader and larger audience checking it out too, through webcasts and coverage. All eyes are on Apple these days.
Also... no mention of resolution independence, even though apparently it's in there, according to folks that have the WWDC Beta? Zero mention of iLife updates?
There were some good parts. I thought Phil Schiller was extremely humorous and effective showing some of the fun things you can do with Leopard iChat (though Steve did talk over him a bit). And Steve drew a wonderful contrast with Windows with his "multiple versions of Leopard will be available... but all will be priced at $129 and contain everything... we think most people are going to pick the Ultimate version..." joke.
But overall, Steve seemed a little flat and off, like he was going through the motions a bit. He also massively overused the word "cool". He's gotta be careful, or its going to become to him what the word "hot" is to Paris Hilton.
Don't get me wrong, though... Steve a little bit off is still light-years better than Gates or Ballmer on their best public-speaking day. I just think that the case for Leopard was stronger than Steve presented, ironically. Didn't think I'd ever say that.
He might be well-served by taking one more crack at it when Leopard launches in October.