Will your Mac actually run OS X 10.8 Mountain Lion? Depends on its vintage.
If you're new to the Mac, Apple's use of "vintage" identifiers (the introduction date for a model of Mac) can be a little startling to those used to actual model numbers. For example, you might own a Mac Mini from July 2011, or a MacBook Air from October 2010. You'll see these dates when you shop for hardware and when you need to upgrade.
Here's a listing from Apple's store, highlighting the release date of the laptop's model.
That vintage information is used in various ways to support your unit and helps identify what features the hardware can provide, since each generation of Macs brought a certain cluster of capabilities to the table.
To look up your Mac's vintage, do the following. Select About this Mac from the Apple menu, then click the More Info... button. This brings you to a system overview screen, like the one at the top of this post. Here, you'll find the name and generation of your Mac.
Some users like to know the model name as well as the vintage, although this is not needed for Apple compatibility charts. To find out the exact Model Identifier in use, then click the System Report button. In the Hardware Overview screen, you'll find your exact model name (e.g. Mac mini) and identifier (Macmini3,1 for the Early 2009 minis).
Once you know a model's vintage, you'll be able to use that information when checking compatibility at Apple's website. Here is a screen shot from the Mountain Lion technical specifications page, which details which models you'll be able to install OS X 10.8 on.
By knowing your Mac Mini is from early 2009, for example, you'll be assured that you're good to upgrade it to Mountain Lion.
Your Mac's vintage provides an essential way you can identify your unit to look up information on Apple's site or when talking to any of Apple's technical support branches.
For many new Mac owners, your move to Mountain Lion represents your first major upgrade. To help users prepare to make the jump, Steve Sande and I wrote Getting Ready for Mountain Lion, an Amazon/iBooks eBook. It's aimed at first-time upgraders and people looking for hints and tips about smoothing the transition. We're sharing some of our tips on TUAW in a series of posts about the 10.8 upgrade. OS X Mountain Lion will be offered for sale in July 2012 for $19.99.
Thanks, John Jellema