Apple updates their products in a very consistent manner. A Mac comes out at a certain price with certain features. The price and features of that particular Mac stay exactly the same throughout the lifespan of the product. So, if a customer buys on Day #1, they are getting the fastest/newest technology for the dollar. The problem, however, is that 8 months later, on the day prior to its refresh, that Mac costs the exact same money, but contains 8 month old technology. (link)

Although based on rumors and second-hand reports, the Guide is pretty dependable, especially since Apple (AAPL) switched to Intel chips. Intel (INTC) is quite open about its product plans, and Apple tends to switch to their newest processors in a fairly predictable timeframe. (Although as MacRumors notes, Intel’s switch to the Nehalem microarchitecture, due late this year, could stretch out some Apple product cycles.)

To see the full 2008-2009 Buyer’s Guide, click here. This is a summary of their recommendations:

• iPod classic: Buy only if you need it – Approaching the end of a cycle
• iPod touch: Neutral – Mid product cycle
• iPod nano: Buy only if you need it – Approaching the end of a cycle
• iPod shuffle: Buy – Product recently updated
• Mac mini: Don’t Buy – Updates soon
• Mac Pro: Neutral – Mid product cycle
• MacBook: Buy – Product recently updated
• MacBook Pro: Buy – Product recently updated
• iPhone: Buy only if you need it – Approaching the end of a cycle
• LCDs: Don’t Buy – Updates soon
• Xserve: Buy – Product recently updated

There’s lots more information in the full Buyer’s Guide, including historical release dates, days since update and links to recent news.

One caveat: you take a risk when you buy a computer on Day #1, as MacRumors suggests. You might want to monitor Apple’s discussion boards for few weeks to see what problems emerge. Let the company and the users who like to live on the bleeding edge work out the kinks before you buy.