Macworld is claiming that tests performed on Apple’s new Intel based Mac don’t back up claims
that it delivers a 2X performance improvement over G5-based iMacs. Macworld did, of course, perform its tests using some of the earliest Intel-ready Mac apps and ones running under Apple's slow Rosetta technology, so there is indeed the possibility that Intel Macs will be a good bit zippier once everything is more developed. Whilst the Intel based Mac might not live up to Apple’s claims, there is some good news.
Macworld Lab’s tests do show that the new Intel-based iMac is faster than the iMac G5 when running native applications. However, we found that those improvements are generally much less than what Apple claims is a 2x improvement in speed.
Instead, our tests found the new 2.0GHz Core Duo iMac takes rougly 10 to 25 percent less time than the G5 iMac to perform the same native application tasks, albeit with some notable exceptions. (If you'd prefer, that makes the Core Duo iMac 1.1 to 1.3 times as fast.)