iMac G5 (Courtesy of Apple)
As of 2006 Apple is gradually replacing all its models with new models that use Intel processors instead of Apple's traditional IBM PowerPC processors. IBM has made the PowerPC processors for Apple since 1998. Not that I would want to, but you also can run Windows on Apple computers.
I was excited when I first heard Apple's claimed speed increases. Then l read that Intel processors don't run all my software correctly. For professional users it's going to be a bit of a science experiment until all our professional software is re-written to run natively on the Intel chips.
Today PhotoShop CS2 has to run in an interpreter mode, which therefore runs more slowly than it does on older Macs with native PowerPC processors!
In short, don't buy an Intel machine if you run a lot of PhotoShop, which I'm sure you all do. Wait till Adobe introduces CS3 to run correctly on the Intel processor, or stick with an older machine.
The good news is that the Intel machines will run better and better and better as time goes on. I experienced this with the Dual G4 PowerMac I bought in 2000 with OS9. OS9 wasn't smart enough to use both processors, but when OSX came out my machine suddenly ran twice as fast! Unlike Windows, Macs run better as they get older because the newer software improves them. If you're coming from a much older machine, like my 800 MHz iBook, you (or I) will be fine with a new Intel processor since it will run OK today, and really start to scream as you and I buy updated software versions. If you still are running PhotoShop 7 don't bother with Intel machines unless you also plan to update to CS3.
See Apple's info here. Even Aperture won't run properly on Intel machines until v1.1 which is expected mid-March 2006.
When I read the slow speeds of the Intel processors running Photoshop tested on other websites I decided to buy my Quad with the PowerPC processors. I'll let others worry about buying new versions of software that aren't even written yet.
See more from me about Apple Computers