Macworld has some speed tests on the new Intel-based iMac. In short, speed boosts in the real world (viz. the average user’s experience) are really no where near the 2x that Apple has been claiming. Apps and functions generally perform better if the app is a Universal Binary app, but non-native apps running under Rosetta are essentially crippled, which is to be expected since Rosetta is an emulator. The article concludes:
That’s one reason why Apple’s initial speed claims of doubled performance (with some tests running showing as much as a 3x speed boost) were so breathtaking, since they were coming from a chip meant to run small and cool. Unfortunately, our tests suggest that the remarkable results of Apple’s published tests aren’t reflected in most of the real-world applications we tested. Based on our initial tests, the new Core-Duo-based iMac seems to be 10 to 20 percent percent faster than its predecessor when it comes to native applications, with some select tasks showing improvement above and beyond that.
Potential iMac buyers who predominantly rely on applications that aren’t available in Universal versions (or, for that matter, those who rely on Classic, which is incompatible with Intel-based Macs) will likely not be interested in these first Intel systems. Running a handful of programs in Rosetta seems reasonable, but if you rely on numerous applications that aren’t yet Universal, it’s probably wise to wait.
Now that we have Intel-based Macs in the wild, we can finally start getting hints of how this transition period is going to be. Right now, it seems that at least the transition period will not have the wow factor Steve Jobs thinks we will get. Of course, the end result may put Apple machines in a much better position than if they had stuck with IBM’s chips.