This is an interesting topic that has come up a few times across many forums. I just want to make my point clear about the issue. Mac OS X Leopard will be a Universal Binary, which means, it will run on existing PowerPC and Intel systems. The big question is, which PowerPC systems will be supported. I say, support will be a reflection of Tiger today, USB and Firewire required and the lack of certain features and functionality that might require more memory and graphics/processing power. Also, I think using the transition to PPC is a bad example, remember, Apple has compiled a native Intel version of OS X for the past 5 to 6 years, 10.0, .1, .2, .3, .4 and .5. So, the transition is not as tumultuous with Intel as it was then, its pretty much finished with Tiger already since we have had that on machines released in January. Its delivering the systems, and Apple has pretty much accomplished much of that leaving the MacPro, Xserves and possibly a future revisioned eMac as the next candidates for Intel processors. But the main issue of concern among many persons is when will OS X stop supporting PPC systems. First of all, lets get something straight, the speculations about 10.7, .8, .9 are becoming a bit absurd, the farthest I think Apple has gone with the Decimal releases was 8.6, so, lets be realistic and say, the last OS X will stop at version 10.6. This does not mean Apple will give up on the cat names, but I am sure they want a refresh in the versioning at some point. (I know Mac OS 11 sounds bad, but it has been on my mind a few months now, and I am beginning to get accustomed to it, its possible they could bring back a classic and call it "System 11" or just Mac OS with less emphasis on the versioning. Back to support, I think PowerPC support will continue even after version 10.6, but possibly be dropped for PPC G3 and G4 systems, but continue on for G5 systems. We must take into account the G5 is a powerful 64-bit architecture and their are folks out their with G5 Dual core systems, 8GBs of RAM, and these systems are still upgradable. Also, I am sure Freescale will continue to provide upgrades for existing G3/G4 owners. Apple also said, they will finish all production of PPC by "2008". I guess you all forgot that. So, OS X has a long life on PPC, and because Apple's development processes is different from Microsoft's, support for PPC can continue without being prohibitive to Apple's R&D. Remember, Apple has development of Universal binaries down to a T (they have been practicing since OS 10.0 , and the fast release to market of Pro apps such as Aperture, Final Cut Studio are great examples of that. Ultimately, support will come down to the third party developers, and I believe Leopard will be a starting point for minimum requirements in the future. Note though, this is not hardware barrier, but a software one, which means, the Utlimate decision goes back to hardware support by OS X in the future versions. Thanks for taking the time to read.