WithTea, while the Intel Macs are expected to start coming out second quarter of '06, they're going to hit the laptop lines first, then the other slow machines, and won't be replacing the high-end chips until '07 sometime. So it depends a bit on what kind of machine you want, as well as the "guinea pig" factor. Chances are the first few months are going to see an unusually high amount of problems as subtle bugs rise to the surface. If you're wanting a high-end machine I'd say buy before the chip switch happens. If you want a *Book though, you're probably best off waiting until a couple months after the chip switch, and seeing what reviewers are saying about the new chip functionality.
As far as the chip "speed", wako is completely wrong. Saying one chip is faster than another because it's got higher clock speed is like saying one car is better than another because it's got bigger wheels, and therefore goes farther each time the wheels turn. It completely ignores how the vehicle is actually built. CPUs have become monstrously complicated beasts. Tens of millions of transistors making up hundreds or thousands of processing subsections. Issues such as step count for floating-point calculations, # of registers, branch misprediction rates, percentage of null commands, and other highly technical geek stuff factor in. Intel's chips have higher clock rates than IBM's or AMD's, yet quite often perform worse due to focusing more on speed than complexity. When the G5's came out, they were undisputedly faster than anything Intel or AMD were selling. By now that edge has been lost, although the G5's are hardly behind on a dollar/performance basis.
A lot does have to do with how the software is written too. Mac has stuff like Final Cut that works faster than anything you can get for Windows. However your 3D realtime games are nearly universally better on Windows machines because the people who make them don't spend much time trying to optimize the huge graphics load for the Mac chipset. Finally, if what you do consists of web surfing, mail, basic photo editing... you're hardly ever going to use the full capacity of the chip anyways. So shrug and accept that some huge video file might take a half second longer to load into Quicktime, and appreciate the fact that your computer will pretty much never crash. How many half-seconds does it take to make up the time it takes to reboot Windows once?
BTW, between the official divx codec, 3ivx and FFusion, I can watch 99% of all .avi filetypes. Alll three are free, just drop into your /Library/Quicktime folder and start Quicktime. VLC Player does run more efficiently though, so it's a better choice for watching divx files with really high bitrates.
