Well, since jobs only showed us 10 new features and I dont have a copy of Leopard, I can only guess that he covered the "top 10" new features. Based on what I saw, Im just not that jazzed. Certainly nothing was shown that warranted the hype the past several months or Jobs quote of "Leopard will be worth the wait" So far it "looks" a tad-bit nicer and has a few new "gee-whiz" features but other than that? Where is the meat? Why is a upgrade going to be that important, isn't Tiger the cats meow? I'll get it when I buy a new system (bundled) but just wont be buying a retail boxed copy when its released.
When you buy is up to you. The plus side of waiting for a new computer to purchase is that you get a new iLife too hopefully.
I'll give my honest opinion about Leopard. First let me state that Steve Jobs did once again fool users by over hyping the Top Secret features. I love good marketing as much as anyone but that simply was a bad idea. Expectations rose too much.
Leopard is truly way beyond Tiger. Tiger to me was the first usable OS that didn't have many "glaring" issue but just a bunch of small ones. When I look at Leopard I'm seeing some very nice things.
Quicklook- is simply going to change how we access our documents. I realized the power but Apple has impressed me with the demo. Who doesn't have a folder of poorly named documents that need a quick "preview" to see the contents? I do this all the time. With Quick look all I'll need to do to view contents or grab info quickly is select the file and hit the space bar. So if I know I only need a small piece of data I'm not firing up the whole application just to get it. It really is a major feature
Finder/Dock/Stacks- Evolutionary but welcomed. I believe in the "Sidebar" paradigm. I think many users are familiar with the left side of applications or websites providing navigation and hierarchy. I'm all ready reading reports that the pains with network shares and the Finder are gone. Coverflow is useful for folders with small amounts of files IMO.
Spaces/iChat- I doubt I'll use these but I'm ok that they're there. iChat would get more use if it does remote control. Spaces sounds great but memory isn't exactly free and I just can't leave applications open all day.
Mail/iCal/Sync- I really like the enhancements to mail. The HTML stuff isn't bad but the headliners to me are the integration with iCal and To Dos. iCal now has a new API that 3rd parties software vendors can use to read/write data. Sync services should finally mature and work right. I'm not sure if I'm going to have an iPhone soon but the pieces are coming together.
I don't want to blather but Jobs simply didn't cover all that is Leopard. You heard nothing about Resolution Independence, He didn't cover the spiffy QT Kit and QT Capture stuff that take over a lot of Quicktime functionality. He didn't cover the new text capabilities of Leopard, He didn't cover the OpenGL 2.1 or the threaded UI rendering which eliminates many of the beachballs and lag in Tiger.
This is a Developers conference and they get access to all the stuff still under NDA. My recommendation is that if someone has a slower G4 or plans to upgrade their Mac in the next year then by all means hold out. But if you like computing and value efficiency then Leopard is a no brainer. From a developmental standpoint it's so significant...enough developers are delivering some apps as Leopard only and I've seen statements from Omnigroup and the Scrivener developer that their next major updates to some of their products will be Leopard only joining Textmate 2.0, Delicious Library 2.0, and Flysketch as the initial Leopard Only crew AFAIK.
There's nothing in Leopard that one cannot easily understand at first glance but don't let the simple stuff fool you. It's like Expose, you see it demoed and it doesn't fully translate to the end user how cool it really is in use.