It was just over three years ago that Apple introduced the first Macintosh using an Intel processor. Up until that day, Apple had always used Motorola, or IBM/Motorola, chips in the Mac. Newer, and faster, processors were not coming fast enough from Motorola so Apple made the decision to switch to Intel. The new chips from Intel ran faster, used less power, and generated less heat than the PowerPC (PPC) chips they replaced (the G5 tower had 9 fans). The end of the PowerPC Mac is near.
The PPC chip the 60x series, G3, G4, and G5 was, at the time, a viable processor and could hold their own against the Intel Pentium II, III and IV. However, Intel was starting to make some advances in their chip designs, especially in the mobile market. Heat was becoming a major problem in most desktops, even more so in laptops. In the beginning of 2005, Apple had G5 processors in the iMacs and towers, but their laptops, the PowerBook and iBook, were still running on older, and slower, G4 processors. The inability of IBM/Motorola to produce a G5 processor that would fit in a laptop was a major incentive to switch to Intel.
Apple announced in June of 2005 that it would switch to Intel processors starting in 2006 (the same processor used in the myriad of Windows PCs. This transition went very smoothly, which is pretty amazing since it was not just a simple chip exchange (the PowerPC chip and the Intel chip essentially speak different languages). One thing that made this transition go so smoothly was the fact that Apple had the foresight to create, but not release, an Intel version of each release of OS X 10.0, 10.1, 10.2, 10.3, and 10.4. When the first Intel Mac was introduced in January of 2006 it had a seasoned Intel version of OS X Tiger.
Another part of this smooth transition was something Apple called Rosetta (as in Rosetta Stone). It was a translator built into Tiger that allowed an Intel Mac to run PPC based software. Apple also came up with software for developers allowing them to create a single version of their software that would work on both a PPC and an Intel Mac. This was dubbed Universal Binary.
The transition to Intel was completed in record time. Apple's proposed finish date was to have all Macs transitioned to Intel by the end of 2007. Amazingly, they were able to finish this feat even before the end of 2006, meaning they upgraded all Mac models within 12 months time.
All Macs have been shipping with Intel processors now for over two years. They have gone from the original Core Solo and Core Duo chips to the faster Core 2 Duo chips. The top-of-the-line Mac Pro started out with two dual-core Intel Xeons, creating a four processor Mac workstation, and now come with two quad-core Intel Xeons, creating the first eight processor Mac workstation. Faster Intel chips are in the works for future machines, proving that Apple's decision to leave PPC was for the best.
Over the last three years, companies like Adobe, Microsoft, and others rewrote their software to work natively with the Intel processor. This of course did not happen over night, but Apple created software and other tools to help make this transition possible is the shortest time. Apple itself had to rewrite its own software, iLife, iWorks, Final Cut Express, Final Cut Studio, etc. to work with the Intel processor.
The rising popularity of the Mac and the fact that they are using the same processors as Windows machines brought back some of the gaming companies. A company like Electronic Arts, a major Windows games company, can reuse much of the same software code thus making it easier to create a Mac version of a PC game.
Later this year Apple should release the next version of OS X codenamed Snow Leopard (the current OS X 10.5 is named Leopard). This new version is reported to not introduce any new 'major' features. Instead, Apple has decided to take the current OS X, Leopard, and refine it. Rumors about Snow Leopard say that Apple has rewritten much of the code for the OS and other parts like Mail, iChat, Address Book, Safari, etc. and optimizing them, making them smaller in size and run faster. Snow Leopard is also stated to be a full 64-bit OS.
Now that Apple and others are advancing software to take full advantage of the Intel processor, there comes a time when we will have to let go of the past. This time is coming very soon. If you take a look at some of the latest games and other software, even Apple's own software, you will see that more of it is requiring an Intel based Mac. The newest versions of Apple's iLife and iWork will work on both PPC and Intel Macs, but some functions only work on Intel Macs. Even the Internet is starting to be Intel only. The 2008 Olympics could be seen online, but only if you had an Intel based Mac. The same holds true with services like Netflix where you can watch instant movies online, if you have an Intel Mac.
It is quite clear that the PPC Mac is quickly coming to an end. This doesn't mean that a PPC based Mac is worthless; it just means that soon you will no longer be able to update it any further. A dual G4 Mac or a G5 Mac is still a nice 'general purpose' computer. If you have plenty of software and your Mac does everything you need it to do then I wouldn't worry about this too much. If you are the type who likes to, or needs to, run the latest software and OSes, then you will want to use an Intel based Mac.
Since OS X 10.6, Snow Leopard, is not shipping yet, it's hard to say whether it will require an Intel processor or if it will also run on certain PPC Macs. If it only runs on an Intel processor, then we can be fairly certain that more software will start requiring an Intel processor and the end of the PPC Mac will not be near, it will have arrived.