MacSpeedZone posts their benchmarks for the Dual Core Intel iMac and claims that Macworld's initial test were misleading:
This is where the Macworld "First Lab Tests" article falls a little flat ... obscuring the processor capacity vs processor usage problem inherent with mutiprocessor machines (or multi-core ... same difference). Using Macworld's logic we could argue, given the data above, the Quad G5 Power Mac is only 14% faster when running some of Apple's own applications. We think that this is misleading, as we pointed out.
They post a comparison chart, taking into account percentage of processor usage as a guide.