The problem isn't the raw speed of Apple's 2.0 Ghz Intel-based dual-core iMacs. According to CNET Anchordesk's Rafe Needleman, it's the inability of buyers to get at that performance through natively written applications. Wrote Needleman in a recent Anchordesk newsletter:
Intel-powered iMac fails performance tests: This is an awkward time for Mac buyers. If you buy an Apple iMac Core Duo today, you'll get a machine that will be a great all-around performer--eventually. While it runs new applications (such as the iLife suite) quickly, existing applications run slowly. We won't be able to recommend the iMac for general use until apps such as Photoshop are released for the new design. For workstation-class performance today, check out the Power Mac G5 Quad, but know the architecture will soon be obsolete.