You will be getting the update disks, NOT the full version that Apple is selling for $129. If you ever need to re-install Leopard you will not be able to do it with update disk unless you install Tiger (or the previous OS) first. And that's a pain in the ass.
This is the Apple world not Windows.
A. The "upgrade disk" for Leopard is the retail version of Leopard.No difference.
B. When you buy a Mac you get whats called "install disks".Usually 2.
The first disk normally holds the O/S and disk two has iLife'08.
There IS NO difference between an "upgrade disk" and a "retail disk"
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When Tiger was released Developers were the last to get a hard copy.Consumers got it first.Developers got Tiger client and server in a sleeve mailed to them around the same time the monthly ADC mailing goes out.
And I believe the GM of Tiger wasn't available for download until a week after the retail version was shipped.It may have been the same way with Panther and Jaguar before that.I forget.
Companies like Adobe already have a GM build of the newest version.
When Apple declares a GM they normally send copies to the top-tier vendors like Adobe and Microsoft to insure compatibility.
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Apple will make sure Leopard is at your door on the 26th because it's sort of a tradition in Apple land that everybody gets to go ooooooo and ahhhhhhh at the same time.Plus or minus a day or two depending on whether or not the end user lives in a major market area.If you live out in the sticks you can expect a delay of a day due to the irregular routing.
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In the case of Apple's O/S this is one time when it's really "mostly" made in the USA with duplication plants stamping out the disks as we sit here typing.This is one reason people in the U.S. normally receive shipment first.