Back in May, when we published our feature story "The New Rules for Buying a Mac", we tried to help prospective Mac buyers by tossing out the old rulebook and writing a new one, debunking lots of long-held myths along the way.

Now that the holidays are upon us, many of you might be considering the purchase a new Mac system. And in the intervening time, Apple has updated several of its models, particularly in its laptop line. (See our summaries of Apple's current Mac offerings.) So here's an updated set of buying tips based on the Macs that are available today.

The iMac: Power at a Low Price

For years, Apple's high-end Power Mac desktop systems were a great--and perhaps the only--choice for a wide variety of Mac users. Many Macworld editors, for example, would never have considered anything less when buying a new Mac. And when the iMac made its debut, it was an underpowered system that serious power users would never consider.

But things have changed. As the iMac entered the Intel era, something interesting happened: those lower-end systems became powerful in their own right, down to the dual-core technology that was previously the provenance of the highest-end machines. Now almost every Mac is suitable for general use, even by a wide swath of power users.

For most mainstay applications, the high-end iMac and MacBook Pro models are plenty fast for power users. Even Adobe Photoshop, a heavy-duty program that conventional wisdom has long argued should be run only on a high-end system, works acceptably well on just about any Mac (unless you're editing gigantic files).

Expandability: Do You Really Need It?

If you're a Windows PC user switching to the Mac, you may be frustrated by the fact that almost none of Apple's systems offer the upgrade flexibility that most desktop PCs do. You can upgrade a PC's graphics card, its hard drive, and even its processor and motherboard relatively easily. But on the Mac, those sorts of upgrades are much less common. You can't just replace a Mac's processor the way you can a PC's, there aren't as many Mac-compatible video cards out there, and Macs have never had the sort of "build your own" following that cheap PCs have.

For many computer users, expandability is a little like insurance. What if you want to add a hard drive? Or a new video card? Or more RAM? Or a faster processor? If your computer is truly expandable, you can theoretically stave off obsolescence with a series of canny upgrades over its lifetime. But most people don't really take advantage of their computers' expandability--especially the unique form of expandability the Mac Pro offers.